Marsh on the move: bringing environmental education into the classroom

By Josie Storm, Christine Parisek, Brian Williamshen, Caroline Newell, Sarah Yarnell, Kim Luke, Jake Shab, and Erin Tracy

This spring, a group of researchers and students at the Center for Watershed Sciences (“Watershed”) organized a community engagement event at a local high school, with the help of our Diversity, Equity, and Inclusivity Committee. At Watershed, we recognize a tremendous value in opportunities that not only inspire youth to forge meaningful connections with their local watershed, but also enable greater access to outdoor experiences. Initiatives like these have the potential to foster a deeper understanding and appreciation of the natural world, especially in the coming generations. We value experiential learning, especially when it enhances each individual’s connections and interactions with nature. These experiences are known to have numerous benefits to health and well-being, and have the potential to play a pivotal role in nurturing lifelong positive relationships with the environment (Miller 2005; Soga and Gaston 2016).

We hoped this outreach effort would inspire students to become more curious about their local watershed. Many participants had never visited their local marsh, Suisun Marsh, before, nor were aware they could visit the marsh to view tule elk, or realized how many birds live and rely on the marsh. There are over 60,000 birds that use the marsh, with over fifty different bird species alone (Moyle et al. 2014). Suisun Marsh is the second largest estuarine marsh on the west coast of North America (Mount and Kimmerer 2022), and it is a migratory corridor for many fishes, including the native Chinook salmon, Sacramento splittail, and prickly sculpin, and non-native striped bass, white catfish, Mississippi silverside, and various shad species (O’Rear and Moyle 2019). Indeed, in partnership with the California Department of Water Resources, Watershed researchers have been sampling and monitoring fish populations in the marsh since the 1980s (O’Rear et al. 2021).

Caroline Newell teaching students how to cast a fishing rod

On May 25th and 26th 2023, we visited Fairfield High School to bring nature into the classroom and connect students with their local marsh. We designed the event similar to one we hosted in 2022. We went to Fairfield High School to show students how to assess water quality in the marsh, as well as some tips and tricks for birding and fishing in the marsh. With increasing urbanization, and as opportunities for people (especially youth) to connect with nature decrease (Pyle 1993; Miller 2005; Hartig et al. 2014; Soga & Gaston 2016; Skar et al. 2016; California Coastal Conservancy 2017), it is important to show how nearby places like Suisun Marsh generate value for communities. By bringing the marsh to the classroom, we hoped to show what kinds of opportunities the marsh could offer, both for fun as well as potential career paths.

Dr. Sarah Yarnell and students holding up a seine net.

Over two days at Fairfield High School, our team discussed with students topics related to the biodiversity and history of Suisun Marsh, careers in environmental field work, outdoor recreation, and methods for catching fish, identifying birds, and measuring water quality for ecological research. Throughout the event, the team talked about their own research work and led hands-on activities for students in Ms. Handa’s classes, ranging from freshman to seniors in advanced-placement (AP). Here, we hoped to inspire interest and curiosity about the flora and fauna that made up the marsh just fifteen minutes away from their school. In addition, the class space became an “open house” at the student’s lunch hour, so that students not in Ms. Handa’s class were also able to come in and explore plant and animal specimens generously provided by the UC Davis Museum of Wildlife and Fish Biology.

Students crowd around Elsie Platzer to touch and look at a fish.

On day one, after some background on the marsh and showing a video that presents some Watershed field sampling techniques in action, students were split into groups to engage in different activities. Caroline Newell, a graduate student at Watershed, led a hands-on activity where she taught students how to use fishing rods (some of which were raffled off for students to take home as prizes) and cast weights into various targets outside the classroom. Although the majority of students had little to no experience with a rod and reel, by the end of the activity they were casting lines all around the lawn outside.

Dr. Sarah Yarnell, a senior researcher at Watershed, also held activities outside and showed students different methods in the scientific collection of fishes, including cloverleaf and minnow traps, and demonstrated using a seine net with help of the students. Employing a PIT tag reader (similar to the instrument used to check a pet’s microchip), Dr. Yarnell illustrated how researchers can track telemetered fish and explained the importance of it.

Inside the classroom, graduate students Elsie Platzer and Erin Tracy showed students fish and invertebrates found in the marsh. There were several species of fish – tule perch, splittail, striped bass, prickly sculpin, and starry flounder – to display the diversity of shapes and life history strategies that fish use to make a living in the marsh. Elsie and Erin answered any questions students had and further explained the biodiversity of the marsh. An often asked question was, “Why is the water so murky?” to which they learned how water clarity changes with decaying and living plants and suspended particles in the water. Students were engaged with concepts of how fish were adapted to the ecosystem that they lived in.

A lucky student wins a fishing pole from the raffle.

On day two, a new cast of Watershed-ers visited the classroom to share their areas of expertise. Four graduate students – Caroline Newell, Kim Luke, Lynette Williams, and Brian Williamshen – and one CDFW employee and Watershed alumnus, Dr. Dylan Stompe, again divided the class for two different hands-on learning stations.

One station was focused on water quality and marsh plants. Students measured different parameters, like salinity, dissolved oxygen, and heavy metal concentrations using an electronic probe and simple color-changing test strips. They also learned how different physical processes, like river flow, can change aspects of the water and how living organisms, like plants and bacteria, change water chemistry and quality. Dylan and Brian showed different plants that are submerged in, emerge from, or live near water, and how they are adapted for survival. Students had the opportunity to touch, visually inspect, smell, and taste the different plant species.

The second station was a crash course in birding (bird watching). Students went outside and first learned how to use binoculars, then applied that skill to play a game of “bird bingo” where students had to identify pictures of birds the volunteers had pasted on walls around the quad. Each student was given a Birds of Suisun guide donated by the San Joaquin Audubon Society to help identify the bird photos, and were encouraged to keep the guides after the activity to continue birding. Throughout the activity Lynette, Caroline, and Kim taught the students about bird migrations and the importance of Suisun Marsh to many different species.

At the end of each class period during the 2-day event, the team raffled away fishing rods, waterproof dry-bags, binoculars, and neck gaiters, giving the lucky winners some tools to help them get started in appreciating and enjoying the outdoors.

Despite being the second largest estuary on the west coast of North America (Mount and Kimmerer 2022), Suisun Marsh is not well known to many, and is often seemingly inaccessible to students in the adjacent city of Fairfield – despite being only ~15 minutes away. We hope we accomplished our goal of exciting students about their local resources and giving them some basic knowledge on outdoor recreation and marsh ecology. If we were able to inspire just a single student, the work to put on this event was well worth it.

“My students enjoyed learning about the history of the marsh and exploring various marsh activities. They were able to see several species of aquatic life for improved understanding of ecological structure. They loved the outside hands-on activities which allowed them to learn fishing and birding skills. These experiences were valuable for students to make personal connections with class curriculum and the important ecosystems that surround them. Some students were inspired to explore natural spaces on their own and others wanted to find volunteer and internship opportunities working in environmental sciences. This was fantastic!” – Heather Handa, Fairfield High School, California

Josie Storm is an Undergraduate Student at UC Davis and Student Assistant at the Center for Watershed Sciences. Christine Parisek is a Ph.D. Candidate in the Graduate Group in Ecology at UC Davis and a Science Communications Fellow at the Center for Watershed Sciences. Brian Williamshen is a Ph.D. Student in the Graduate Group in Ecology at UC Davis. Caroline Newell is a Masters Student in the Graduate Group in Ecology at UC Davis. Sarah Yarnell is a Senior Researcher at the Center for Watershed Sciences. Kim Luke is a Masters Student the Animal Biology Graduate Group at UC Davis. Jake Shab is an Undergraduate Student at UC Davis and Student Assistant at the Center for Watershed Sciences. Erin Tracy is a Ph.D. Student in the Animal Biology Graduate Group at UC Davis.

A word cloud illustrating the frequency of key terms used in post- experience student feedback responses. Larger font indicates words used in higher frequency in the responses.
Generated using

Further Reading (mostly related to the marsh):

Durand, J. 2021. A Recorded Conversation with Dr. Peter B. Moyle.

Hobbs, J. and P. Moyle. 2018. Will Delta Smelt Have a Happy New Year?

Manfree, A., and P. Moyle. 2014. Planning for the inevitable at Suisun Marsh.

Mount, J. and W. Kimmerer. 2022. The Largest Estuary on the West Coast of North America.

Moyle, P. 2020. Eating Delta Smelt., P.B., A.D. Manfree, and P.L. Fiedler. 2014. Suisun Marsh: Ecological History and Possible Futures. University of California Press.

Moyle, P., D. Stompe, and J. Durand. 2020. Is the Sacramento Splittail an Endangered Species?

O’Rear, T., and P. Moyle. 2019. Remarkable Suisun Marsh: a bright spot for fish in the San Francisco Estuary.

O’Rear, T., J. Durand, and P. Moyle. 2021. Suisun Marsh fishes in 2020.

Rypel, A.L. 2021. Sometimes, studying the variation is the interesting thing

Stompe, D.K., P. Moyle, A. Kruger, and J. Durand. 2020. Fish surveys in the estuary: the whole is greater than the sum of its parts.

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Hidden links between aquatic and terrestrial ecosystems: part 1 – Sierra Nevada lakes

By Nicholas Wright

A small alpine lake in Yosemite National Park. Photo credit–Mick Haupt, public domain

This blog is the first in a three part series on ecological subsidies that will appear throughout summer and fall ’23.

It’s easy to think of aquatic and terrestrial organisms inhabiting entirely separate worlds–they experience distinct biophysical conditions, interact with different ecological communities, and are imperiled by divergent environmental threats. But there are far more ecological connections between land and water than meets the eye. Organisms and organic matter move back and forth between terrestrial and freshwater ecosystems and are consumed or die in one or the other, transferring energy and nutrients in a phenomenon known as a trophic subsidy. Subsidies primarily flow from more productive food webs to less productive ones, at times allowing abundant life to exist in otherwise unproductive habitats. Some of these linkages are small and surprising, and others are more profound. Understanding cross-system flows of energy and nutrients is essential for conservation during a time of breakneck environmental change.

We start our story with a small lake, clear as glass and cold as ice, nestled among a dark conifer forest and surrounded by towering granite peaks. This lake, like thousands of others in the Sierra Nevadas, is fairly small–around the size of two football fields–and was carved by glaciers. The water is so clear because little algae can grow due to the cold temperatures and lack of nutrients. Without much algal production, there’s almost no food for consumers being produced in the lake–but that doesn’t mean there’s no food.

In spring, as the sun hits the mountain slopes, the thick snowpack starts to melt. The water percolates down into the mulchy top layers of the forest soil, which is rich with decomposed organic matter from pine needles and dead grass, fallen trees, and animal carcasses. As the water flows it picks up and dissolves organic matter and then carries it deeper into the soil and the upper layers of crumbling bedrock, flowing downhill until it meets a headwater stream that eventually flows into an alpine lake. The dissolved organic matter provides a terrestrial trophic subsidy, a flow of energy from forest to lake that feeds aquatic consumers. This subsidy offers the most significant food source in the lake at this time of year, supporting a food web of microbes, zooplankton, aquatic insects, frogs, and fish.

One study on cross-system subsidies in the Sierra’s showed that, during spring, lakes are so reliant on this terrestrial trophic subsidy that they are actually heterotrophic, meaning more organic matter is consumed than produced, which causes lakes to release CO2 into the atmosphere (Piovia-Scott et al 2016). In late spring and early summer, as days get longer and warmer, algal growth increases. In these warm days, as the snowpack melts away and stream flows decline, less terrestrial organic matter is carried into the streams and lakes. During this period the algal growth makes Sierra lakes become autotrophic, which means they produce more organic matter than they consume and they begin absorbing CO2 from the atmosphere. Over the course of an entire year, mid-elevation lakes that receive lots of organic matter subsidies from their forested watersheds tend to be net heterotrophic, while lakes above the treeline, where watersheds are predominantly bare rock, receive a much smaller flux of terrestrial organic matter and are typically slightly net autotrophic. 

The greatest fluxes of terrestrial organic matter in the Sierras come from wet meadows (Piovia-Scott et al. 2016). These meadows, located in mountain valleys, are often created by beavers damming streams and they sequester lots of carbon in their reach peaty soils (Yarnell et al 2019). Water percolates slowly through these heavy soils, turning the riparian meadows into vital wetlands, even during periods of drought, and leaching dissolved organic matter into alpine streams and lakes. 

Organic matter from decomposing vegetation that feeds the bottom of the food chain is not the only terrestrial trophic subsidy to the lake. Swarms of flying insects fall into the water or hover just above it, where they make easy prey for fish. In Castle Lake, in far northern California, terrestrial insects were found to provide about a third of the food items some fish species consumed (Vander Zanden et al. 2006). In fall, as the algae grow slower and little food is produced within the lakes, insects continue to provide a stable food source that allows larger populations of fish to survive than would otherwise be possible.

Massive swarm of black-and-red seedbugs in the Eastern Sierras. Photo credit–CBS News

Once the most abundant run in California, Spring-run Chinook Salmon historically depended on terrestrial insect subsidies, but has now declined throughout streams of the Sierras. The cold water, gravel substrate, and swarms of insects made Sierra streams an ideal habitat for salmon parr, which have a longer freshwater residence time than other California salmon, to rear in great numbers before migrating downstream out of the mountains and into the Sacramento River. However, throughout the last two centuries mining operations degraded many of the salmon’s spawning grounds and the construction of dams made many of the Sierra streams inaccessible to salmon. Now the remaining Central Valley spring-run salmon must scrape out a living in a few lower-elevation reaches of streams in the Sierra foothills and Sutter Buttes and the population has been federally listed as ‘threatened’.

Nicholas Wright is junior specialist in the Johnson-Jeffres research group.

Further Reading:

Piovia-Scott, J., Sadro, S., Knapp, R.A., Sickman, J., Pope, K.L., and Chandra, S. 2016. Variation in reciprocal subsidies between lakes and land: perspectives from the mountains of California.Canadian Journal of Fisheries and Aquatic Sciences, 73, 1691–1701.

Pope K.L., Piovia-Scott J., and Lawler S.P. 2009. Changes in aquatic insect emergence in response to whole-lake experimental manipulations of introduced trout. Freshwater Biology, 54(5): 982–993.

Rypel, A.L. 2022. Nature has solutions…What are they? And why do they matter? California Water Blog

Vander Zanden M.J., Chandra S., Park S.-K., Vadeboncoeur Y., and Goldman C.R. 2006. Efficiencies of benthic and pelagic trophic pathways in a subalpine lake.Canadian Journal of Fisheries, 63(12): 2608–2620.

Vredenburg V.T. 2004. Reversing introduced species effects: experimental removal of introduced fish leads to rapid recovery of a declining frog. Proceedings of the National Academy of Sciences, 101(20): 7646–7650.

Yarnell, S. M., Pope, K., Burnett, R., Wolf, E., Wilson, K. (2019) An experimental study of the ecohydrologic and carbon sequestration benefits of beaver dam analogue restoration techniques in Childs Meadow, CA, USA. AGU Fall Meeting 2019.

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Putah Creek’s rebirth: a model for reconciling other degraded streams?

By Emily Jacinto, Nann A. Fangue, Dennis E. Cocherell, Joseph D. Kiernan, Peter B. Moyle, and Andrew L. Rypel

Putah Creek is an aquatic ecosystem embedded within a truly human-dominated landscape. Photo of Lower Putah Creek near Davis CA, January 2011 (photo credit: Peter Moyle).

It’s hard to look at native fishes in Putah Creek and not grin a little. Be it a Sacamento Pikeminnow (below), a Sacramento Sucker, a Tule Perch, or even a Chinook Salmon – Putah Creek has become a treasured resource in our local community. The stream and its riparian areas are a nature refuge for local residents, a field site for teaching students, and increasingly a science lab for studying restoration.

A native Sacramento Pikeminnow captured from Putah Creek. Photo credit: Andrew Rypel

As often discussed on this blog, California’s freshwater ecosystems face numerous challenges due to human activities (Moyle and Rypel 2023, Rypel and Moyle 2023, Rypel 2023). These are not just California problems, they are global problems, especially in regions that share our Mediterranean style climate. Putah Creek exemplifies the scope and challenges of human pressures on the environment. It is a reconciled stream tucked into a landscape fully dominated by humans (above picture). In this blog, we delve into results from our recent paper (Jacinto et al. 2023). The paper expands on those of Keirnan et al. 2012 and examines trends in the Putah Creek fish assemblage since the 1990s. It shows the multiple ways in which the assemblage has improved following implementation of the Putah Creek Accord, and suggests similar strategies could be used to recovering ecological capacity in other degraded streams.

Damming and Draining Putah Creek

In 1957, a large capacity dam (Monticello Dam, below left) was constructed on Putah Creek. The dam dramatically transformed the natural flow regime, channel structure, geomorphic processes, and overall ecological character of the stream. In addition, a diversion dam (Putah Creek Diversion Dam, below right) was constructed ~13km downstream from Monticello Dam that diverts flows into a canal for use in agriculture and urban areas. Over time, a reduction in downstream flows, particularly during summer months, resulted in an aquatic assemblage completely dominated by warm-water nonnative species. Meanwhile, native species struggled to survive and were relegated to subordinate roles. Anadromous fishes, such as Chinook salmon, which were once present, but in variable numbers (Shapovalov 1947), were extirpated. During the 1990s, the creek regularly dried for prolonged periods because of lack of flow releases and drought.

An Accord for Ecosystem Rehabilitation

Recognizing the massive ecological degradation caused by reduced flows below the dams, a court-mediated Accord was ratified in 2000. The Accord stemmed from a lawsuit (Putah Creek Council vs. Solano Irrigation District and Solano County Water Agency, Sacramento Superior Court Number 515766) that was filed to provide a more natural flow regime under Section 5937 of the California Fish and Game Code which requires that fish populations below dams be kept in “good condition” (Börk et 2012; Moyle et al. 1998). The Accord aimed to restore a more natural flow regime that specifically benefited native and anadromous fish species. At the time, legal issues focused on keeping the creek from drying, developing spring flows for native fish (which are needed for spawning and for dispersal and survival of juveniles), creating fall attraction flows for spawning Chinook salmon, and generating high flows to displace nonnative fish and to promote natural channel processes. Implementation of the Accord marked a significant turning point in the rehabilitation of the creek.

How has the Putah Creek Assemblage Changed Over Time?

Number of native and nonnative fish species have changed over time in Putah Creek. Upstream sites (A-D) have seen major declines in nonnative (gold) and no change or increases in native species (blue). Downstream sites (E-F) have largely remained unchanged. Initiation of the Accord is indicated by a vertical line.

Since the 1990s, researchers have collected standardized fish community data at a series of sites along the longitudinal profile of Putah Creek. To assess the long-term effects of the restoration, we analyzed the full comprehensive dataset spanning pre- and post-Accord years. In particular, we focused on the numbers of native and nonnative species and overall stability of the ecosystem.

Analyses revealed compelling results that generally highlight success and limitations of the approach. Richness of nonnative species consistently declined at every monitoring site following the implementation of the Accord. In contrast, native species richness either increased or remained stable over time. Notably, the most upstream sites demonstrated the strongest recovery of native species richness, with all upstream sites surpassing nonnative richness over time. Yet in more downstream reaches, the recovery rate of native species decreased.This finding suggests recovery of the native assemblage was more pronounced closer to flow releases and habitat rehabilitation activity.

Rank-abundance curves showed that species evenness (inequality) remained low throughout the study. Therefore, stream rehabilitation activities did not change the underlying assembly dynamics of the fish community. Rather, it reordered the species to be increasingly dominated by natives than nonnatives. And again, there was a notable shift in dominance from nonnative to native species in the upstream sites, coinciding with more intensified rehabilitation efforts.

Rank-abundance curves describe many key aspects of ecological community dynamics, including richness (number of species) and evenness (slope of the curve). In this figure, rank–abundance curves are shown for every site across time – each year is presented by a single curve. We show that proportional abundance changed for native (solid blue circles) versus nonnative (solid orange circles) species (Panels A-F, left). The center (b) and right (c) panels show the same curves, but highlight two native (Rainbow Trout = solid blue circles and Prickly Sculpin = solid green circles), and two nonnative (Largemouth Bass = solid orange circles and Common Carp = solid red circles) species. Initiation of restorative flows from the Accord is indicated by a gray vertical line.
Mean rank shifts, a measure of ecosystem stability, have declined over time. Thus, Putah Creek is becoming an increasingly stable fish assemblage.Again, initiation of the Accord is indicated by a vertical line.

Finally, we document another encouraging finding – increased stability (=less variability) in the assemblage over time. Mean rank shifts in abundance, which measures variability in species ranks, decreased over the years, indicating a more stable and balanced ecosystem with time. This shift towards greater stability is attributed to the increasing dominance of native species; however the exact mechanisms for the stability remain unclear and worth further study.

Putah Creek as a Model for Recovering Ecological Functions

Adult Chinook salmon ascending Putah Creek, late fall 2022. Photo: Anne Boyd.

The rebirth and recovery of Putah Creek stands as a compelling model for others seeking to enhance the functionality of degraded freshwater ecosystems. Perhaps of most public attention was the return of anadromous salmon to the system circa 2015 (Willmes et al. 2020, Willmes et al. 2021). Thus while salmon numbers decline and crash across the Pacific Rim, in Putah Creek, salmon numbers appear to be increasing. Combined with the fish assemblage story outlined here, these lines of evidence suggest something quite positive has indeed occurred.

By prioritizing native species and implementing measures to recover key aspects of natural flow regimes, rehabilitation efforts in Putah Creek have been successful. These changes functionally reversed a dominance by nonnative species and bolstered recovery of native fishes. Similarly degraded stream ecosystems abound in California. And some streams (e.g. the Kern River in Bakersfield) still run dry even though these streams are still below dams and subject to California Fish and Game Code 5937. What is perhaps most stunning is the extent of ecological changes that occurred with just a marginal improvement in flows. 95% of flows in Putah Creek are still diverted for human use. Thus, the change described here represents that which can be done with only 5% of flows. Just imagine how our ecosystems would respond with more! These findings suggest there is much that can be accomplished with an environmental flows approach (Yarnell et al. 2015), and perhaps the voluntary agreements, if executed thoughtfully.

Putah Creek between Davis and Winters CA. Photo: Andrew Rypel

Emily Jacinto was a graduate student at UC Davis and is now an Environmental Scientist with California Department of Fish and Wildlife. Nann Fangue is a Professor and Chair of the Department of Wildlife, Fish & Conservation Biology at University of California, Davis. Dennis E. Cocherell is a Lab Manager and Staff Research Associate in Wildlife, Fish, and Conservation Biology at the University of California, Davis. Joseph Kiernan is a Research Scientist at NOAA based at the Southwest Fisheries Science Center. Peter B. Moyle is a Distinguished Professor Emeritus at the University of California, Davis and is Associate Director of the Center for Watershed Sciences. Andrew L. Rypel is a Professor of Wildlife, Fish, and Conservation Biology and Director of the Center for Watershed Sciences at the University of California, Davis.

Further Reading:

Börk, K., J. Krovoza, J. Katz, and P. Moyle. 2012. The Rebirth of California Fish & Game Code Section 5937: Water for Fish. University of California Davis Law Review 45: 809–913.

Collins, S.L., M.L. Avolio, C. Gries, L.M. Hallett, S.E. Koerner, K.J. La Pierre, A.L. Rypel, E.R. Sokol, S.B. Fey, D.F.B. Flynn, S.K. Jones, L.M. Ladwig, J. Ripplinger, and M.B. Jones. 2018. Temporal heterogeneity increases with spatial heterogeneity in ecological communities. Ecology 99: 858-865.

Jacinto, E., N.A. Fangue, D.E. Cocherell, J.D. Kiernan, P.B. Moyle, and A.L. Rypel. 2023. Increasing stability of a native freshwater fish assemblage following flow rehabilitation. Ecological Applications 33: e2868.

Kiernan, J. D., P. B. Moyle, and P. K. Crain. 2012. Restoring native fish assemblages to a regulated California stream using the natural flow regime concept. Ecological Applications 22:

Marchetti, M. P., and P. B. Moyle. 2001. Effects of flow regime on fish assemblages in a regulated California stream. Ecological Applications 11: 530–9.

Moyle, P. B., M. P. Marchetti, J. Baldrige, and T. L. Taylor. 1998. Fish health and diversity: justifying flows for a California stream. Fisheries 23: 6–15.

Moyle, P.B., and A.L. Rypel. 2023. Monster fish: lessons for sturgeon management in California.

Rabidoux, A., M. Stevenson, P.B. Moyle, M.C. Miner, L.G. Hitt, D.E. Cocherell, N.A. Fangue, and A.L. Rypel. 2022. The Putah Creek fish kill: learning from a local disaster.

Rypel, A.L. 2023. Facing the dragon: California’s nasty ecological debts.

Rypel, A.L., and P.B. Moyle. 2023. Hatcheries alone cannot save species and fisheries.

Shapovalov, L. 1947. Report on Fisheries Resources in Connection with the Proposed Development of the United States Bureau of Reclamation. California Fish and Game 33: 61–8.

Willmes, M.,  E.E. Jacinto, L.S. Lewis, R.A. Fichman, Z. Bess, G.P. Singer, A. Steel, P.B. Moyle, A.L. Rypel, N.A. Fangue, J.J.G. Glessner, J.A. Hobbs, and E.D. Chapman. 2021. Geochemical tools identify the origins of Chinook Salmon returning to a restored creek. Fisheries 46: 22-32.

Willmes, M., A. Steel, L. Lewis, P.B. Moyle, and A.L. Rypel. 2020. New insights into Putah Creek salmon.

Yarnell, S. M., G. E. Petts, J. C. Schmidt, A. A. Whipple, E. E. Beller, C. N. Dahm, P. Goodwin, and J. H. Viers. 2015. Functional flows in modified riverscapes: hydrographs, habitats and opportunities. Bioscience 65: 963–72.

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Can Sacramento Valley reservoirs adapt to flooding with a warmer climate?


Englebright Spillway during the 1997 flood

Clementime Dam on the North Fork American River overtopping in 1997. Photo by Rand Schaal.

by Jay Lund and Ann Willis

Editor’s note: This is a blog that was originally posted on 6/25/17. Since publication of the blog, there has been interesting newer research about running the San Joaquin rim dams for “functional flows” (Willis et al. 2022). This work also shows there is also an important component about flood operations, and the limits of dams for achieving such goals. Dr. Willis is now the California Regional Director for American Rivers. Dr. Lund is now Vice Director at Center for Watershed Sciences.

Much has been written on potential effects and adaptations for California’s water supply from climate warming, particularly from changes in snowpack accumulation and melting, sea level rise, and possible overall drying or wetting trends.   But what about floods?

In a paper in the journal San Francisco Estuary and Watershed Science, we along with co-authors from the US Army Corps of Engineers review much of the literature to date and examine how Shasta, Oroville, and New Bullards Bar reservoirs might adapt to floods in a warmer climate, including a climate that is either wetter or drier.

Oroville Spillway during the 1997 flood

A torrent of water flowing from the Oroville Spillway during the 1997 flood

Since no one knows exactly what future floods will look like, the nine largest floods from the historical record were hydrologically modified to be warmer and either wetter or drier, using the National Weather Service hydrologic model used for flood forecasting.  These many modifications to past major floods were then run through a US Army Corps of Engineers’ model for flood operation of these reservoirs to evaluate what might happen, given the way we currently operate these reservoirs.  The results were both reassuring and disturbing.

1. Warming generally worsened flood inflows into reservoirs.  Even with less precipitation, warmer conditions often increased flood inflows to reservoirs.  When more precipitation fell as rain, rather than snow, and more existing snowpack melted, flood volumes increased.  This was particularly true for historical storms that were “cold”, where much of the precipitation was held as snowpack.  Warm storms, which historically produced less snow, were less affected by warming.

2. Reservoirs with flood operating rules that respond to the wetness of their watersheds seemed to adapt well to changes in climate, even fairly severe changes in temperature and precipitation.  This was true for Shasta and Oroville Reservoirs, whose existing flood operation rules vary with moisture conditions upstream.  This shows that existing reservoirs may have considerable ability to accommodate flooding effects of climate warming.

3. Reservoirs with flood operating rules that do not respond to upstream conditions may perform poorly with climate warming.  For example, New Bullards Bar’s flood rules do not change with upstream snowpack and wetness conditions.  For many plausible climate changes, modifications of past floods overtopped this dam, a potentially catastrophic flood risk for downstream residents.

Large uncertainties are common when dealing with both the future and the weather.  Nevertheless, some things can be known, or at least strongly suspected and supported, from reasoning that is organized, refined, and tested using computer modeling.

Accommodating changes in climate with changes in operating rules can often require changes in reservoir outlets (which can be costly) and changes in federal operating policies and authorizing legislation (which can be protracted and difficult).  Nevertheless, it is comforting to know that existing policies for some reservoirs seem to do well with changes in climate, and that making other reservoirs more reactive to upstream wetness conditions might make them more resilient to changes in climate, even before we know what the changes are.  Such changes in policies, while politically awkward and requiring some expense, appeared likely to be less expensive than major reservoir expansions or the costs of a major flood.

In terms of floods, climate warming need not mean that the sky is falling.  We are likely to have considerable ability to respond effectively, but in some cases, we will likely to need to make major changes.  Appropriate preparations will not be easy, but they should be possible with capable institutions at the federal (US Army Corps of Engineers), state (DWR, Central Valley Flood Protection Board), and local (counties, cities, and levee districts) levels.

Jay Lund is the director of the Center for Watershed Sciences. Ann Willis is a staff researcher at the Center for Watershed Sciences.

Further reading:

Willis, Ann D; Lund, Jay R.; Townsley, Edwin S.; Faber, Beth A (2011), “Climate Change and Flood Operations in the Sacramento Basin, California,” San Francisco Estuary and Watershed Science, July, Vol. 9, No. 2, 18 pages.

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Endangered Freshwater Fishes: Does California Lead the World?

By Peter B. Moyle & Robert A. Leidy

Some endemic fishes of California: Little Kern Golden Trout (top left). SONCC Coho Salmon (top center). Santa Ana Speckled Dace (top right), Desert Pupfish (bottom right), Sacramento Perch (bottom, middle), Sacramento Splittail (bottom left).

See Moyle and Leidy (2023) for much more detailed version of this essay.

Few things give the authors of this essay more pleasure than swimming in a California stream on a hot summer day, wearing a mask and snorkel, and observing diverse native fishes behaving naturally. But being able to watch such fishes may be a passing phenomenon, not only here, but globally. Freshwater habitats are disappearing or being rapidly modified, a reflection of the ever-expanding demands of people, accelerated by global climate change. Not surprisingly, there is a global freshwater biodiversity crisis, of which fish are one of the most conspicuous indicators. There is widespread agreement that the crisis is real (e.g., Dudgeon et al. 2006; Strayer and Dudgeon 2010; Darwell et al. 2018, Tickner et al. 2020).

We started to document this crisis over 30 years ago (Moyle and Leidy 1992) when we concluded that, conservatively, 20% of the world’s freshwater fishes were already extinct or in severe decline towards extinction. Six years later, Leidy and Moyle (1997) confirmed this estimate using better information. In our most recent iteration, Moyle and Leidy (2023) concluded that “…without extraordinary measures, at least 40-50% of all freshwater fish species will be extinct in the wild or close to it by the end of the century, if not sooner (p. 201).” In the analysis, we relied on readily available data from the International Union for the Conservation of Nature (IUCN), which attempts to keep track of the status of all species of plants and animals. IUCN (2012) has nine categories for species status: extinct, extinct in the wild, critically endangered, endangered, vulnerable, near-threatened, least concern, data deficient, and not evaluated. Critically endangered, endangered, and vulnerable species are those ‘threatened with extinction’. Definitions of status categories are found in IUCN (2012) and Moyle and Leidy (2023).

The number of unique freshwater fish species on Earth is currently estimated to be over 18,000 (51% of all known fishes) and climbing (IUCN Red List 2022). According to IUCN, almost 3000 species (23% of the 13,276 species assessed) are threatened with extinction. These fishes are distributed among all major taxonomic orders, showing that they occur in freshwater habitats worldwide and are taxonomically diverse. Half of all assessed fishes are widespread or abundant, so they are not threatened with extinction and are classified by the IUCN as of “least concern”. Unfortunately, another 2556 fish taxa (19%) are ’data deficient’, lacking sufficient information for IUCN to assess extinction risk. The comparative lack of information on threatened fishes is reflected in the scientific literature on freshwater fishes, which is primarily about game fishes (Guy et al. 2021).

So how does California compare with the rest of the world in the proportion of its fishes on a pathway to extinction? The comparison of IUCN evaluations with California’s provides a test of both systems because the California freshwater fish fauna is comparatively well-documented, and the state is geographically well-defined. Of the 131 native taxa recognized, 81% are endemic to the state or share watersheds between just two adjacent states. We would not consider any of the native fishes to be ‘data deficient’, and the complete known fauna has been evaluated independently from the IUCN evaluations, using what we call the California Method for Status Evaluation of Fishes (Leidy and Moyle 2021). The method relies on combined scores of 1-5 for each of seven metrics, based on existing data and expert opinion (e.g., area occupied, estimated adult abundance). The method allows short and long-term trends to be evaluated rapidly (Moyle et al. 2011, 2015, Leidy and Moyle 2021, Moyle and Leidy 2023) and retrospective analyses are possible (Figure 1). To make the comparison, we first examined the status of California fishes as evaluated by IUCN, which mainly considers full species. Our list of California fishes includes 82 full species, 42 (51%) of which have been evaluated by IUCN. The IUCN found that 15 (36% of full species evaluated) are threatened with extinction (Vulnerable+Endangered+Critically Endangered); 3 of the 42 species were extinct in California, but still extant outside the state, and two endemic species were globally extinct (Clear Lake Splittail, Thicktail Chub).

Status of California Freshwater Fishes, 1974–2021 (based on Moyle et al., 2015 with updates from P. B. Moyle, unpublished data, November 2020). The fish status numbers for 2021 reflect updates by Moyle (unpublished) based on new information, including genetic studies revealing cryptic species and the most recent status information. From Leidy and Moyle (2021).

For comparison, we examined California’s list of recognized freshwater fish taxa as of 2020 (131 taxa, 81% endemic, Leidy and Moyle 2021). This list includes 100 taxa with formal species or subspecies designations, seven undescribed subspecies, and 24 Distinct Population Segments (as defined by the federal Endangered Species Act of 1973). When we rated the status of all extant species in California using the California Method, 63 (49%) were scored in categories reasonably equivalent to the three IUCN categories lumped together as threatened. In short, our evaluation of the status of all native fish taxa resulted in about twice as many freshwater fishes regarded as threatened with extinction than the IUCN evaluations would indicate. However, when threatened percentages of fishes evaluated are compared (36% for IUCN vs. 49%), the numbers are more comparable. The IUCN percentage is close to the 32% of California fishes formally listed under state and federal Endangered Species Acts and the 30% of all freshwater fishes assessed by the IUCN.

Given that only about half of the 9800+ freshwater fishes have been assessed, 30% probably represents a conservative number of globally threatened fishes (ca. 3000 species). California, therefore, is a world leader in having its endemic freshwater fishes likely to be driven to extinction by the end of the century. This prediction becomes even more likely when the effects of global warming are considered, along with the increased demand for water and other resources by the planet’s expanding human population. Right now, we are facing the extinction of Delta Smelt, which exists today mainly as the result of a captive breeding program. The Winter Run Chinook Salmon also relies on captive breeding and is somewhat better off because a few fish still spawn naturally, albeit in the highly modified outflows of Shasta Dam.

Our conclusion: The best available evidence indicates that, if present trends continue, at least 40-50% of all freshwater fish species will be extinct in the wild or close to it by the end of the century. Aquatic habitats worldwide instead will support highly homogenized, if depauperate, fish faunas, part of novel ecosystems dominated by people and by non-native species such as common carp, tilapia, largemouth bass, a catfish or two, and mosquitofish. A few hardy native fishes might serve as a distinctive part of each local assemblage, reminders of past species richness (Moyle and Leidy 2023).

The question then becomes, Can California be the leader in developing conservation strategies that reverse the decline of freshwater ecosystems and their diversity, including fishes? We think the answer to the question is ‘yes,’ but whether California citizens and their leaders have the will to do so is questionable, as our inadequate response to climate change shows (even though it is better than most of the rest of the USA). Widely recognized among aquatic ecologists and biologists (and other professionals) is that climate change is accelerating the need for large-scale actions to slow or even reverse the rapid decline of fish abundance and diversity. However, the severity of the global situation is underestimated by most people. The ever-increasing trend in use and abuse of our fresh waters means that extinction of fish species on a large scale is a near-certainty in the foreseeable future. Given the scope of the problems and conflicts that fish conservation engenders, large-scale solutions are unlikely to arise, such as those discussed by Moyle and Leidy (2023) and references therein. Meanwhile, more local actions might save a few species from extinction.

We prefer optimism to the gloomy vision projected above because healthy waterways for fish are also good for people, as the Clean Water Act has long been recognized. An optimistic vision includes systematically protecting and managing diverse rivers, streams, lakes, and wetlands in each global region to ensure that some of our aquatic diversity survives into the distant future. This would include managing whole watersheds for their biota, with native fishes as indicators of success. Such Freshwater Protected Areas cannot just exist as incidental parts of terrestrial protected areas but must be a central focus of a system of aquatic reserves. Successful Freshwater Protected Areas will need to be linked in a broad scheme of stream and lake management that integrates the needs of humanity with those of fishes and their ecosystems.

We need the fishes and the fishes need us.

Peter Moyle is an emeritus professor in the Center for Watershed Sciences, University of California, Davis. Robert Leidy is a research scientist affiliated with the Department of Environmental Science, Policy and Management at the University of California, Berkeley.

Further reading

Closs, G.P., P. L. Angermeier, W. R. T. Darwell, and S. T. Balcombe. 2015. Why are freshwater fishes so threatened? Pp. 37-75 In G. P. Closs, M. Krkosek, and J.D. Olden eds. Conservation of Freshwater Fishes. Cambridge University Press

Darwell, W. R.T. and J. Freyhof. 2015. Lost fishes: who is counting? The extent of the threat to freshwater fish biodiversity. Pp.1-36 In G. P. Closs, M. Krkosek, M. and J. D. Olden. eds., Conservation of Freshwater Fishes. Cambridge University Press

Darwell, W. R. T., and 22 co-authors. 2018. The Alliance for Freshwater Life: A global call to unite efforts for freshwater biodiversity science and conservation. Aquatic Conservation: Marine and Freshwater Ecosystems: 2018: 1-8.

Dudgeon, D. et al. 2006. Freshwater biodiversity: importance, threats, status and conservation challenges. Biological Reviews 81:163-182. DOI:

Guy, C.S., Cox, T.L., Williams, J.R. et al. 2021. A paradoxical knowledge gap in science for critically endangered fishes and game fishes during the sixth mass extinction. Scientific Reports 11, 844.

Harrison, I. et al. 2018 The freshwater biodiversity crisis. Science 362: 1369.

International Union for the Conservation of Nature (IUCN). 2012. Red List Categories and Criteria: Version 3.1. Second Edition. Gland, Switzerland and Cambridge, UK: IUCN. iv+32pp.

Leidy, R. A., and P. B. Moyle. 1998. Conservation status of the world’s fish fauna: an overview. Pp.187-227 In P. L. Fiedler and P. M. Karieva, eds. Conservation Biology for the Coming Decade. N. Y.: Chapman and Hall

Leidy, R. A. and P. B. Moyle. 2021. Keeping up with the status of freshwater fishes: a California (USA) perspective. Conservation Science and Practice 3(8), e474. 10 pages.

Moyle, P.B., J. V. E. Katz and R. M. Quiñones. 2011. Rapid decline of California’s native inland fishes: a status assessment. Biological Conservation 144: 2414-2423.

Moyle, P. B., and R. A. Leidy. 1992. Loss of biodiversity in aquatic ecosystems: evidence from fish faunas. Pp. 128-169. In P. L. Fiedler and S. A. Jain (Editors), Conservation Biology: The Theory and Practice of Nature Conservation, Preservation, and Management. New York: Chapman and Hall.

Moyle, P.B., J. D. Kiernan, P. K. Crain, and R. M. Quiñones. 2013.Climate change vulnerability of native and alien freshwater fishes of California: a systematic assessment approach. PLoS One.

Moyle, P.B. and A.L. Rypel. 2023. Monster fish: lessons for sturgeon management in California.

Rypel, A.L., 2023. Facing the dragon: California’s nasty ecological debts. California WaterBlog, June 11, 2023.

Strayer, D.L. and D. Dudgeon. 2010. Freshwater biodiversity conservation: recent progress and future challenges. Journal of the North American Benthological Society 29: 344-358. DOI: 10.1899/08-171.

Tickner, D.,et al. 2020. Bending the curve of global freshwater biodiversity loss: an emergency recovery plan. BioScience 70: 330–342.

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Facing the Dragon: California’s Nasty Ecological Debts

By Andrew L. Rypel

“Every time you borrow money, you’re robbing your future self.” ~N. Morris

Pre-dam view of the Tuolumne River stretching across Hetch Hetchy Valley in the early 1900s. Photo from Taber 1908.

When I was younger, a close friend of mine struggled with a crippling debt. It was during that unique period shortly before and after college graduation. He had, in relatively short order, maxed out three credit cards, plus taken out a line of credit as a ‘student loan’. The borrowed money was being used to fuel a series of bad habitats, including early 20s party life. I watched my friend, and just didn’t know what to do or how to help. Quickly, the debt and bills and interest stacked up to a breaking point.  Finally, the collectors were after him. Eventually, he told the parents, and together, they crafted a plan to solvency. It was hard. He moved home, changed his day-to-day behaviors, and took an entry level job as a teller at the local bank. It took almost two years of living at home, an abrupt end to college life, and placing any savings above minimum needs into paying back the debt. He did it though, and went on to graduate school and a successful career.

Being young at the time, watching this unfold was a formative experience. It taught me the important and timeless lesson: There is no free lunch. Recently, I have been reflecting on California’s intractable environmental woes: its ecosystems, water, and the communities who rely on them. For many, these problems seem too difficult to solve, so much as to classify them as ‘wicked problems’. Sometimes however, solutions require fresh perspectives. For example, there is much we can glean from economics and study of debt. In this essay, I explore the concept of ecological debts, the extent to which California has amassed ecological debt, and what a return to solvency might look like.

What are ecological debts?

The concept of ecological debts arose in the early 1990s by two independent teams of researchers focused on environmental liabilities transmitted to future human generations (Robleto and Marcelo 1992, Jernelov 1992). Over the years, applications of the environmental debt concept has been quite broad, with many applications showing connections to environmental justice. For example, many of the most degraded ecosystems are associated with marginalized communities and/or stolen lands. During the mid-90s, ecologists began to focus on variants on these concepts, like “extinction debts” (Tillman et al. 1994). That is, that extinctions often occur years or generations following habitat fragmentation. Speed of extinction following fragmentation can therefore be fast or slow, depending on the severity of amassed debt (Kuussaari et al. 2009). I think of ecological debts as impacts and/or resource consumption by humans in excess of the natural productive capacity of ecosystems. The concept of environmental debts seem unpopular with conventional economists, perhaps because it conflicts with the notion of economic growth as being unlimited. Yet as an ecologist by training, it is obvious to me time and again, that natural resources have limits, and that without proper management, ecosystems and species just collapse.

Examples of ecological debts abound. They are especially obvious in highly modified landscapes. Given poor agricultural practices for example, landscape modifications fragment and alter wildlife habitat, strip top soils from land, and send nutrients barrelling downstream into lakes and estuaries where toxic algal blooms ensue (Bailey 2020). Similarly, overfishing or poaching tends to benefit a select few, but the impacts of these activities are felt broadly (Carrizo et al. 2017). In other cases, we all take out a note from nature together. For example, when we collectively drive cars, we exact a toll on our climate and the metals, minerals, and land that support them.

Map of the hypoxic zone in the Gulf of Mexico, sometimes referred to as the ‘dead zone’. These impacts are an example of an ecological debt from nutrient enrichment in the Mississippi River basin. Figure from Rabalais and Turner 2019.

Climate change is just another example of ecological debt, at the planetary scale. Scientists knew as early as the late 1800s that even minor changes to the composition of the atmosphere could substantially alter surface temperatures. Original theories of climate change based on carbon dioxide were formulated in the 1950s (e.g., Plass 1956). US Congressional hearings were held in the 1980s on the topic. All the while, a carbon dioxide debt continued to relentlessly build. And while some continue to deny the existence of climate change altogether, many opposed to climate action, often admit that climate change is real, but hold that the financial cost is too great to do anything about it right now. In essence, folks acknowledge the debt, but don’t want, or know how, to begin paying it back.

Has California amassed ecological debt?

Yes. As a student of the native freshwater species of the state, the scope of the debt that I am most familiar with is large and scary. A review of the status of native California fishes shows that, since the 1970s, the number of stable species has declined, while the number of threatened and endangered species continues to increase (Quiñones & Moyle 2015). The number of extinct species has not increased to the same degree, yet. This discrepancy between the number of threatened species and the number of extinct species clearly illustrates the status of our debt, and the stakes. This is an extinction debt – and it’s growing.

Status of California’s native fish fauna over time. Data adapted from Quiñones & Moyle 2015.

We see the scope of our ecological debts clearly when examining the story of California salmon. California was once the epicenter for the salmon industry in the USA. Chinook salmon abundance in the Central Valley might have approached 2 million fish annually (Fisher 1994). In 1880, 10 million pounds of salmon were caught within the Sacramento-San Joaquin Delta alone, roughly equivalent to 750,000 salmon (Yoshiyama et al. 1998). The most recent projection for all Sacramento River fall-run Chinook in 2023 is just 169,767 adults; a result that prompted closure of the fishery this year. Spring-run Chinook salmon were historically co-dominant with fall-run Chinook salmon, and were especially abundant in the San Joaquin Basin (Rypel et al. 2021). Spring-run Chinook salmon are now federally threatened under the US Endangered Species Act.

Historical catches of large salmon were once common in CA (Peter Palmquist collection)

Several impacts and ecological loan generating activities are responsible for these trends, none of which happened overnight. Dams were a major factor. Construction of the major dams blocked access for salmon to all the best spawning habitats. Then at lower elevations, water was extracted from the rivers, and the wetlands/floodplains summarily drained. At times, so much water was extracted that rivers would simply run dry. This one-two combo finally did in the San Joaquin River spring-run Chinook population (Rypel et al. 2021; Hause et al. 2022).

Occasionally, it is suggested ‘people didn’t know what they were doing back then’, implying that impacts of dams on salmon were unknown. This is false. Just as with climate change science, numerous reports painstakingly detail the impending impact of planned dams on salmon (e.g., Brennan 1938; Hanson 1940). Rather, the thinking seemed to be that the ecological loan would be worth it. Whether it was because of war time needs, or the need to grow the economy, or our tendency to undervalue nature, this was the decision. There was also hubris; for example, that hatcheries could effectively mitigate the problem. For this reason, most large rivers in California’s Central Valley with natural runs of Chinook salmon, now also have a production hatchery (Katz et al. 2013). But the hatcheries didn’t work (Rypel and Moyle 2023), and salmon continue to decline throughout California and the Pacific rim. These trends unfolded over generations and centuries (Munsch et al. 2022), often so long ago that we don’t recognize or grapple with the reality that these are debts from previous generations that we are still paying.

Construction work on Shasta Dam in 1942. Photo by Russell Lee from the US Library of Congress.

California’s ecological debts surround and haunt us. From salmon to delta smelt (Moyle et al. 2021), forest management (Hutto 2008), the attempt to eliminate Lake Tulare (Moyle 2023), the decline of the Salton Sea, decisions surrounding water rights (Börk et al. 2022), theft from California’s Indigenous communities (Hanks 2006), groundwater overdraft (Gray 2018), the accumulation of nitrate in groundwater (Harter et al 2012), a global loss of insects (van Klink 2020; Jähnig et al. 2020), and other important axes of biodiversity like freshwater mussels (Rypel 2022) or our herpetofauna (Halstead et al. 2010). All are ecological debts for California that remain unpaid.

What might a plan look like to pay back California’s ecological debts?

As with financial debt, acknowledging the problem is a critical first step. And just as one tries to come to grips with financial debt, a full-scale accounting is essential. This could show where we have borrowed and how much. It could suggest specific areas or actions that might have disproportionately positive conservation outcomes. Such an effort could be a special project, a blue ribbon report, or an interagency task force.

Release of spring-run Chinook salmon into the San Joaquin River. Photo from

The good news is we don’t need to reinvent the wheel from scratch. There are many examples we can learn from. The case of Mono Lake comes to mind, where diversions from the lake, including Rush and Vining Creek needed to be stopped. As flows to the lake improved, aquatic habitat and salinity conditions also recovered, and even today, lake levels are actively managed. The San Joaquin River is becoming another example. As the San Joaquin River Restoration Program gains steam, more water and fishes will be in the ecosystem. Recovery will take time, but payments (in the form of additional flows and habitat) are beginning to be made, which in turn is resulting in positive results for salmon (Rypel et al. 2021). The California State Groundwater Management Act (SGMA) is aimed explicitly at solving debts in groundwater levels that have accumulated over decades. These groundwater debts ultimately resulted in subsidence, and ironically reduced capacity to convey surface water. The full socioeconomic impacts of SGMA have yet to be realized, but are large. Does this mean SGMA was a bad idea? Perhaps not, but it illustrates the kinds of hard decisions that sometimes need to be made to repay environmental debts. And of course Putah Creek continues to teach us how ecosystem services can be recovered with modest tweaks to water management (Rypel 2022; Jacinto et al. 2023). Public repayments must be collaborative endeavors – this is why solutions like the salmon-rice project, where growers and conservationists collaborate will be increasingly needed to craft payment structures that actually work in today’s human-dominated landscape (Rypel et al. 2022).

Debts are an unpleasant aspect of life. They are undoubtedly frustrating because, in the case of the environment, loans were taken out by previous generations that may or may not share our contemporary values. Those generations profited from these loans that we still owe, and even worse, engaged in nefarious activities by today’s standards. And in some ways, we have benefited from the debts they incurred. Yet they are debts whose balance comes due nonetheless. Nature continues to unambiguously signal that our existing loans are too heavy, and bankruptcy is on the horizon. California has a history of innovation and problem solving that has defied its critics. Dealing with our ecological debts is one of our biggest current challenges. Just as my old friend had to finally face his financial debt, so must we with ecosystems. Doing so necessitates that we collectively face the dragon and attempt to deal with our ecological problems with clear eyes and a full heart.

San Joaquin River near the Mossdale boat launch. Photo from USFWS/Steve Martarano.

Further reading:

Börk, K., A.L. Rypel, S. Yarnell, A. Willis, P. Moyle, J. Medellin-Azuara, J.  Lund, and R. Lusardi. 2022. Considerations for developing an environmental water right in California.

Carrizo, S. F., S. C. Jähnig, V. Bremerich, J. Freyhof, I. Harrison, F. He, S. D. Langhans, K. Tockner, C. Zarfl, and W. Darwall. 2017. Freshwater megafauna: Flagships for freshwater biodiversity under threat. Bioscience 67:919-927.

Fisher, F.W. 1994. Past and present status of Central Valley Chinook salmon. Conservation Biology 8: 870-873.

Gray, B. 2018. The public trust and SGMA.

Halstead, B. J., G. D. Wylie, and M. L. Casazza. 2010. Habitat suitability and conservation of the giant gartersnake (Thamnophis gigas) in the Sacramento Valley of California. Copeia 2010:591-599.

Hanks, R. A. 2006. This war is a war for life: the cultural resistance among southern California Indians, 1850-1966. PhD Dissertation. University of California Riverside.

Hansen, H. A. 1940. Preliminary report on an investigation to determine possible methods of salvaging the Sacramento River salmon and steelhead trout at Shasta Dam. Stanford Ichthyological Bulletin 1:199– 204.

Harter, T., J. R. Lund, J. Darby, G. E. Fogg, R. Howitt, K. K. Jessoe, G. S. Pettygrove, J. F. Quinn, J. H. Viers, D. B. Boyle, H. E. Canada, N. DeLaMora, K. N. Dzurella, A. Fryjoff-Hung, A. D. Hollander, K. L. Honeycutt, M. W. Jenkins, V. B. Jensen, A. M. King, G. Kourakos, D. Liptzin, E. M. Lopez, M. M. Mayzelle, A. McNally, J. Medellin-Azuara, and T. S. Rosenstock. 2012. Addressing Nitrate in California’s Drinking Water with a Focus on Tulare Lake Basin and Salinas Valley Groundwater. Report for the State Water Resources Control Board Report to the Legislature. Center for Watershed Sciences, University of California, Davis. 78 pp.

Hause, C. L., G. P. Singer, R. A. Buchanan, D. E. Cocherell, N. A. Fangue, and A. L. Rypel. 2022. Survival of a threatened salmon is linked to spatial variability in river conditions. Canadian Journal of Fisheries and Aquatic Sciences 79:2056-2071.

Hutto, R. L. 2008. The ecological importance of severe wildfires: some like it hot. Ecological Applications 18:1827-1834.

Jacinto, E., N. A. Fangue, D. E. Cocherell, J. D. Kiernan, P. B. Moyle, and A. L. Rypel. 2023. Increasing stability of a native freshwater fish assemblage following flow rehabilitation. Ecological Applications:e2868.

Jähnig, S. C., V. Baranov, F. Altermatt, P. Cranston, M. Friedrichs‐Manthey, J. Geist, F. He, J. Heino, D. Hering, and F. Hölker. 2021. Revisiting global trends in freshwater insect biodiversity. Wiley Interdisciplinary Reviews: Water 8:e1506.

Jernelov, A. 1992. Miljoskulden, En rapport om hur miljoskulden utvecklas om vi ingenting gor. SOU. 1992: 58 Allmanna forlaget, Stockholm, Sweden.

Katz, J., P. B. Moyle, R. M. Quiñones, J. Israel, and S. Purdy. 2013. Impending extinction of salmon, steelhead, and trout (Salmonidae) in California. Environmental Biology of Fishes 96:1169-1186.

Kuussaari, M., R. Bommarco, R. K. Heikkinen, A. Helm, J. Krauss, R. Lindborg, E. Öckinger, M. Pärtel, J. Pino, and F. Rodà. 2009. Extinction debt: a challenge for biodiversity conservation. Trends in Ecology & Evolution 24:564-571.

Moyle, P.B. 2023. Lake Tulare (and its fishes) shall rise again.

Munsch, S. H., C. M. Greene, N. J. Mantua, and W. H. Satterthwaite. 2022. One hundred‐seventy years of stressors erode salmon fishery climate resilience in California’s warming landscape. Global Change Biology 28:2183-2201.

Plass, G. N. 1956. The carbon dioxide theory of climatic change. Tellus 8:140-154.

Quiñones, R. M., and P. B. Moyle. 2015. California’s freshwater fishes: status and management. FiSHMED: Fishes in Mediterranean Environments 1:1-20.

Rabalais, N.N., and R.E. Turner. 2019. Gulf of Mexico: past, present, and future. Bulletin of Limnology and Oceanography 28: 117-124.

Robleto, M.L., and W. Marcelo. 1992. Deuda ecologica. Instituto de Ecologia Politica, Santiago de Chile.

Rypel, A.L., and P.B. Moyle. 2023. Hatcheries alone cannot save species and fisheries.

Rypel, A.L. 2022. Being patient and persistent with nature.

Rypel, A.L., D.J. Alcott, P. Buttner, A. Wampler, J. Colby, P. Saffarinia. N. Fangue, and C.A. Jeffres. 2022. Rice and salmon, what a match!

Rypel, A.L. 2022. Losing mussel mass – the silent extinction of freshwater mussels.

Rypel, A.L., C.A. Parisek, J. Lund, A. Willis, P.B. Moyle, Yarnell, S., and K. Börk. 2020. What’s the dam problem with deadbeat dams?,

Rypel, A.L., G. Singer, and N.A. Fangue. 2021. Science of an underdog: the improbable comeback of spring-run Chinook salmon in the San Joaquin River,

Tilman, D., R. M. May, C. L. Lehman, and M. A. Nowak. 1994. Habitat destruction and the extinction debt. Nature 371:65-66.

Van Klink, R., D. E. Bowler, K. B. Gongalsky, A. B. Swengel, A. Gentile, and J. M. Chase. 2020. Meta-analysis reveals declines in terrestrial but increases in freshwater insect abundances. Science 368:417-420.

Yoshiyama, R.M., F.W. Fisher, and P.B. Moyle. 1998. Historical abundance and decline of Chinook salmon in the Central Valley region of California. North American Journal of Fisheries Management 18: 487-521.

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Water Wasted to the Sea?

By James E. Cloern, Jane Kay, Wim Kimmerer, Jeffrey Mount, Peter B. Moyle and Anke Müeller-Solger

This essay is a condensed version of one that appeared in the journal San Francisco Estuary and Watershed Science (Vol. 15, Issue 2, Article 1), in July 2017.  The complete article with references and author’s contact information can be found at:

If we farmed the Central Valley or managed water supplies for San Francisco, San Jose, or Los Angeles, we might think that freshwater flowing from the Sacramento and San Joaquin Rivers through the Delta to San Francisco Bay is “wasted” because it ends up in the Pacific Ocean as an unused resource. However, different perspectives emerge as we follow the downstream movement of river water through the Delta and into San Francisco Bay.

If we were Delta farmers or administered Contra Costa County’s water supply, we would value how high flows reduce salt intrusion (Jassby et al. 1995) and protect water quality for drinking, growing crops, and meeting other customer needs.

If we were responsible for protecting at-risk species, we would value river water that flows through the Delta to the Bay and ocean because it stimulates migration and spawning of native Chinook salmon, Delta Smelt, Longfin Smelt, and Sacramento Splittail, while also reducing the potential for colonization and spread of non-native fishes (Brown et al. 2016). River flow reduces toxic selenium concentrations in clams eaten by sturgeon, splittail, and diving ducks (Stewart et al. 2013), and it delivers plankton and detritus to fuel production in downstream food webs (Sobczak et al. 2002).

If we managed a Bay Area storm water district or sewage treatment plant, we would value water that flows from the Delta into the Bay because it dilutes and flushes such urban pollutants as metals, microplastics, and nutrients (McCulloch et al. 1970).

If we directed restoration projects around the Bay, we would value water that flows from the Delta into the Bay because it brings sediment required to sustain marshes that otherwise would be lost to subsidence and sea level rise (Stralberg et al. 2011; Schoellhamer et al. 2016). Sediment supplies from rivers also sustain mudflats (Jaffe et al. 2007) used as habitat and probed for food by more than a million willets, sandpipers, dunlins, and other shorebirds during spring migration (Stenzel et al. 2002).

If we fished the Pacific for a living, we would value river flow into the Bay because it carries cues used by adult salmon to find their home streams and spawn (Dittman and Quinn 1996), it brings young salmon to the sea where they grow and mature, and it creates bottom currents that carry young English Sole, California Halibut, and Dungeness crabs into the Bay (Raimonet and Cloern 2016) where they feed and grow before returning to the ocean.

If we liked to romp along the shore or served on the California Coastal Commission, we would value rivers that flow to the sea because they supply the sand that keeps California’s beaches from eroding (Barnard et al. 2017).

Finally, if we were among those who want to conserve California’s landscape and biological diversity, we would value river water that flows to the sea because it creates one of the nation’s iconic estuaries, and sustains plant and animal communities found only where seawater and freshwater mix (Cloern et al. 2016).

Is the fresh river water that naturally flows through the Delta to San Francisco Bay and on to the Pacific Ocean “wasted?” No. The seaward flow of fresh water is essential to farmers, fishers, conservationists, seashore lovers, and government agencies that manage drinking water supplies, restore wetlands, protect coastlines, and clean up sewage and storm pollution. Wasted water to some is essential water to others.

Travis Hiett of USGS measures high flows on the Cosumnes River, December 31, 2022, from the bridge at Michigan Bar. Flows were estimated at 63,700 cfs. USGS Photo by Sue Brockner.

Further Reading

Barnard PL, Hoover D, Hubbard DM, Snyder A, Ludka BC, Allan J, Kaminsky GM, Ruggiero P, Gallien TW, GabelL, McCandless D, Weiner HM, Cohn N, AndersonDL, Serafin KA. 2017. Extreme oceanographic forcing and coastal response due to the 2015-2016 El Niño. Nat Commun 8:14365.

Brown LR, Kimmerer W, Conrad JL, Lesmeister S, Müeller–Solger A. 2016. Food webs of the Delta, Suisun Bay, and Suisun Marsh: an update on current understanding and possibilities for management. San Franc Estuary Watershed Sci 14(3).

Cloern JE, Barnard PL, Beller E, Callaway JC, GrenierJL, Grosholz ED, Grossinger R, Hieb K, Hollibaugh JT, Knowles N, Sutula M, Veloz S, Wasson K, Whipple A. Life on the edge—California’s estuaries. In: Mooney H, Zavaleta E, editors. 2016. Ecosystems of California: a source book. Oakland (CA): University of California Press. p 359-387.

Dittman A, Quinn T. Homing in Pacific salmon: mechanisms and ecological basis. J Exp Biol (1):83-91.

Jaffe BE, Smith RE, Foxgrover AC. 2007. Anthropogenic influence on sedimentation and intertidal mudflat change in San Pablo Bay, California: 1856-1983. Estuar Coastal Shelf Sc 73:175-187.

Jassby AD, Kimmerer WJ, Monismith SG, Armor C, CloernJE, Powell TM, Schubel JR, Vendlinski TJ. 1995. Isohaline position as a habitat indicator for estuarine populations. Ecol Appl 5(1):272-289.

McCulloch DS, Peterson DH, Carlson PR, Conomos TJ. 1970. Some effects of fresh-water inflow on the flushing of South San Francisco Bay—a preliminary report: U.S. Geological Survey Circular 637A. 27 p.

Raimonet M, Cloern JE. 2016. Estuary-ocean connectivity: fast physics and slow biology. Global Change Biology [Internet]. [cited 2017 March 18]. Available from:

Schoellhamer DH, Wright SA, Monismith SG, BergamaschiBA. 2016. Recent advances in understanding flow dynamics and transport of water-quality constituents in the Sacramento–San Joaquin River Delta. San Franc Estuary Watershed Sci 14(4).

Sobczak W, Cloern J, Jassby A, Müeller-Solger A. 2002. Bioavailability of organic matter in a highly disturbed estuary: the role of detrital and algal resources. Proc National Acad Sci USA 99(12):8101-8105.

Stralberg D, Brennan M, Callaway JC, Wood JK, SchileLM, Jongsomjit D, Kelly M, Parker VT, Crooks S. 2011. Evaluating tidal marsh sustainability in the face of sea-level rise: a hybrid modeling approach applied to San Francisco Bay. PloS one 6(11):e27388.

Stenzel LE, Hickey CM, Kjelmyr JE, Page GW. 2002. Abundance and distribution of shorebirds in the San Francisco Bay area. Western Birds 33:69-98. Available from:

Stewart AR, Luoma SN, Elrick KA, Carter JL, van der Wegen M. 2013. Influence of estuarine processes on spatiotemporal variation in bioavailable selenium. Mar Ecol Prog Ser 492:41-56.

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What’s the dam problem with deadbeat dams?

by Andrew L. Rypel, Christine A. Parisek, Jay Lund, Ann Willis, Peter B. Moyle, Sarah Yarnell, Karrigan Börk

*this is a repost of a blog originally published in June 2020.

Damming rivers was once a staple of public works and a signal of technological and scientific progress. Even today, dams underpin much of California’s public safety and economy, while having greatly disrupted native ecosystems (Quiñones et al. 2015, Moyle et al. 2017), displaced native peoples (Garrett 2010), and deprived residents of water access when streamflow is transported across basins. California’s dams are aging and many will require expensive reconstruction or rehabilitation. Many dams were built for landscapes, climates and economic purposes that no longer exist. California’s current dams reflect an accumulation of decisions over the past 170 years based on environmental, political, and socio-economic dynamics that have changed, sometimes radically. Former Secretary of the Interior Bruce Babbitt remarked, “Dams are not America’s answer to the pyramids of Egypt… Dams do, in fact, outlive their function. When they do, some should go.

Is California prepared for updating or removing this infrastructure, and what would be the consequences of inaction?

Fig. 1. Transformation of the West through government funded irrigation. From: Donald J. Pisani, To Reclaim a Divided West: Water, Law, and Public Policy, 1848-1902 125 (University of New Mexico Press, 1992)

We examined the National Inventory of Dams (NID) to assess the state of California’s dams. This database is a large data product curated by the US Army Corps of Engineers and contains information on most large dams in the USA (Fig. 2, 3, Table 1). Across the nation there are 91,468 NID dams, with 1,580 in California. Because there are multiple dams on some reservoirs, we estimate a total of 80,101 and 1,444 NID reservoirs in the USA and California, respectively.

Mean age of USA dams is 59 years old; but mean age of California dams is 72 years (Fig. 3). The 25% oldest CA dams are 93 years or older. California’s total reservoir storage capacity behind NID dams is 45 million acre-feet with a total reservoir surface area of 713,146 acres. For comparison, the total surface area of all managed natural lakes in Wisconsin is 943,130 acres, supporting a massive tourism industry (Rypel et al. 2019). Unfortunately, 1,097 (69%) of California NID dams are listed as high or significant hazards to human communities if they fail (Fig. 2, Table 2). These counts greatly underestimate problematic dams. In the USA, there are hundreds of thousands of smaller (often old) dams that fall outside of state and federal lists, and so are not included in the NID. This issue is broader than just dams too – infrastructure of all varieties is aging, representing a growing problem for humans and wildlife (Börk and Rypel 2020).

Fig. 2A. Map of all California dams in the NID.
Fig. 2B. Map of all NID dams in the contiguous USA. In both maps red circles represent dams classified in the NID as “high hazard” (i.e.,the potential for dam failure or facilities mis-operation to result in loss of human life, in addition to lower risk characteristics such as potential for economic and environmental losses). Gray circles represent all other dams.

Fig. 3. Histograms describing characteristics of dams and reservoirs in the USA and California. All data are from the National Inventory of Dams database. All log transformed data are (Log+1) transformations, however mean values in text boxes are non log-transformed values. Year Dam Completed was cropped at >1750 for ease of viewing.

We have already witnessed examples of the high cost of inaction. Recently in Michigan, two dams (Edenville and Sanford) failed and forced the evacuation of 10,000 residents in the midst of the COVID-19 pandemic – essentially a worst case scenario. Extreme rain in the midwest led to historic flooding in the Tittabawasse and Tobacco Rivers. Federal regulators had worried about failures at the Edenville Dam for 30 years due to an undersized spillway (see related news stories 1, 2, 3, 4).

Table 1. Summary statistics on age and storage capacity of dams and reservoirs in the USA and California.

Fig. 4. Oroville’s failing primary spillway during spring 2017. Photo source:

In California, we recall a near miss when the Oroville Dam spillway failed in early spring 2017. Floods damaged the primary spillway such that the California Department of Water Resources stopped flow over the spillway to better assess damage. Lake levels continued to fill and ultimately overtopped the emergency spillway, triggering unexpected erosion around the emergency spillway and the evacuation of 188,000 residents downstream. An independent forensic report of the Oroville incident highlights several lessons, including the need for periodic review of dam design and performance. Dams in California have failed before and a list of major events can be found here and here. Recent evaluations have indicated that conditions of California dams are below average, with one reporting a statewide grade of “C-” (Moser and Hart 2018;

Table 2. Summary of hazard classifications for USA and California dams based on the NID. The NID defines hazard potentials as: “High” –  dam failure is likely to result in loss of human life. “Significant” – likely no risk to human life, but a likelihood to cause economic and/or environmental losses. “Low” – likely no risk to human life and low anticipated economic and/or environmental losses. “Undetermined” – hazard designation not assigned; here, dams classified as “undetermined” were grouped with dams that had an N/A hazard potential.

Dams also can have catastrophic effects on natural ecosystems, especially in productive and species-rich large rivers (Poff et al. 1997). Dams fragment the hydrologic connectivity of ecosystems, and create massive physical barriers for migratory species, including salmon. American rivers are so extensively fragmented by dams, that Benke (1990) estimated only 42 high quality free-flowing rivers remain in the USA – zero in California. In the Sacramento Valley, abundant spring-run Chinook salmon would once migrate long distances and over-summer high in cold mountain streams. Now, spring-run Chinook salmon are listed under the US Endangered Species Act, largely because of disruptions from dams. In the San Joaquin River, construction of Friant Dam preceded a rapid eradication of spring-run Chinook from this ecosystem. Expensive efforts to reintroduce spring-run Chinook salmon hold promise; but fish are still fundamentally blocked from naturally cold habitats by rim dams. The McCloud River once had all four runs of Chinook salmon, plus steelhead and bull trout. None of these species occur in the McCloud River anymore, and bull trout have gone extinct in California. Helfman (2007) suggested that ~70% of global freshwater fish extinctions can be attributed to “habitat change,” including effects of dams.

Fig. 5. Migratory salmon are strongly and negatively affected by dams. This photo shows the types of habitats that salmon often cannot ascend to in California any longer. “Salmon on spawning beds” by John Cobb 1917 in Pacific Salmon Fisheries. Annual Report to the Secretary of Commerce, 1915-1916, Washington DC. Downloaded from Wikicommons and the Freshwater and Marine Image Bank.

Beyond the catastrophic failures and ecological impacts of individual dams, California’s dams create disastrous outcomes for disadvantaged communities, including Native American Tribes. Tribes along the Klamath have spent years struggling to preserve the river and its sensitive salmon populations. Removing deadbeat dams like the four major dams on the Klamath River along the CA-OR border exemplify the types of projects where removal makes economic sense to dam owners and begins to address damage to indigenous communities of color and aquatic ecosystems. NGOs have long been interested in dam removals like this. However, the slow speed of these removals highlights the complicated details involved in removal. Such experiences suggest efforts addressing aging dams must start early.

The California Division of Safety of Dams (DSOS) has existing responsibilities that include: 1) Performing independent analyses to understand dam and appurtenant structures performance; 2) Overseeing construction to ensure work is being done in accordance with approved plans and specifications; and 3) Inspecting dams on an annual basis to ensure it is safe, performing as intended, and is not developing issues. Roughly 1/3 of these inspections include in-depth instrumentation reviews of the dam surveillance network data. Every state (except GA) has a dam safety program, and the CA program is the largest in the USA. Therefore, the DSOD plays a major role in working with dam owners to identify deficiencies in California. The size of the DSOS program suggests this resource could be leveraged in CA to take a leading role in dam safety. Response to aging dams has been mostly reactive. Studies of dam behavior during earthquakes has been a long focus of research, and such questions are obviously important in California. In a 1977 USGS analysis of dam structural behavior during Earthquakes, half the study systems were in California. Many of the major dam failures in California were triggered by earthquakes.

California is well-positioned to lead in proactively addressing aging dams; however, the window for leadership is likely closing. The challenge will be in developing balanced approaches that prioritize the dams, rivers and people in most need of help (Null et al. 2014). To advance policy on dealing with obsolete dams, we suggest California should:

(1) Form a “California Dams Blue Ribbon Panel”. Given recent experiences in California and nationally, it seems timely for the State of California to take stock and assess the long-term performance of its dam regulation capabilities. Efforts are needed to assist the public, local governments, and dam owners in identifying at-risk dams in need of action. A California dams blue ribbon panel would help develop a framework for decision making that could be applied to dams across the state. The panel’s charge would be to: i) evaluate the state’s existing regulatory framework for evaluating public safety and environmental performance of dams; ii) estimate overall magnitude of current and future dam safety and environmental problems (especially with climate change); iii) recommend improvements to state regulatory capacities and support for owners in terms of dam safety and environmental performance. Panel findings might be published as a white paper for others to use and reference. The panel should have broad representation from multiple stakeholder groups including roles for Native American tribes and other disadvantaged and at-risk communities. Ultimately, a blue ribbon panel and white paper format would produce faster results than a larger task-force style effort, but could lead to a larger effort if necessary.

(2) Develop a structured assessment tool. An objective science-based prioritization framework would be useful. Structured assessments are a class of tools that can more transparently and objectively analyze natural resource management decisions in a careful and organized way (Gregory et al. 2011). Such models are popular in some federal agencies and have already aided decision-making in other areas of CA state government, such as welfare services. A directed action to build such a tool could rapidly aid agencies charged with managing aging dams and scoring restoration projects. Once the tool is available, proposed on-the-ground restoration projects could be scored more transparently. Projects that propose work on high priority dam sites might then be prioritized for funding. Thus restoration projects funded through state bond propositions (e.g., Prop 1 and Prop 68) net the state and its investors the most “bang for their buck”, while simultaneously leveraging science and enhancing transparency and accountability. Improvements to the assessment method could form a way of incorporating new scientific findings or ways of thinking over time.

(3) Revisit existing legal frameworks. Dams sit at the crossroads of state and federal law and so face a complex mess of state and federal laws and regulation. Prominent legal issues will include liability for flooding and for environmental damages associated with dam removal (which will differ between privately and publicly owned dams), environmental reviews mandated under state and federal endangered species and environmental impact laws, and the myriad dam-specific laws. This is an area of active research in environmental law (see here recents legal debates on issues facing dams in the Western USA). Some examples of laws that have legal relevance to the operation and use of dams include the California Fish and & Game Code 5937 – “Water for Fish” (Börk et al. 2012). Additionally, under the authority of the Federal Power Act, the Federal Energy Regulatory Commission (FERC) retains exclusive authority to license non-federal hydropower projects on navigable waterways, federal lands, or areas connected to the interstate electric grid. Opportunities for dealing with deadbeat dams also present themselves during the FERC relicensing process. Indeed this was a critical piece to the removal of the Klamath Dams. Most dams currently face little regulation and receive little attention from policy makers.

(4) Explore reservoirs as novel habitats for declining fishes. Because many California reservoirs contain expansive coldwater habitats, scientists have occasionally suggested reservoirs could be capable of serving as emergency rooms for declining native fishes. Some California reservoirs have developed self-sustaining populations of Chinook salmon (Perales et al. 2015). These populations may be needed as a backup plan in the event a disease or other disturbance afflicts the primary Sacramento River salmon runs. We support this concept and note that some reservoirs and dams may hold hidden value in this regard. Reservoirs successfully managed as novel habitat for native fishes might ultimately be scored higher for dam renovation or repurposing funds.

Every dam is unique and there will be no one-size-fits-all approach. Ultimately dams are owned by entities ranging from the state of California, water agencies and districts, counties, cities, homeowner’s associations, private companies, or private citizens. Hansen et al. 2020 identified that in general dams can be mitigated, renovated, repurposed, or eliminated. In California, dams have been important in controlling water availability, both reducing the frequency of catastrophic floods and making water available for cities and irrigated agriculture in our highly variable Medeterranean climate. They will remain vital in the future, perhaps even more so with anticipated changes in climate. Ultimately, some dams will be fine, some will need to be removed, and some modified. At this point however, an overarching strategy is needed to guide efforts to identify which dams are suited to our uncertain future and which are more risky than worthwhile, then rank them with the best rubric we can devise (e.g..Quiñones et al. 2015). Planning for aging dams is not unlike planning for a pandemic. It seems as though you don’t need it…until you do.

Fig. 6. The upper Klamath River in Oregon was once accessible to salmon migrating from the Pacific Ocean through California. The Klamath dam removals promise to reconnect some of these habitats. Photo by Bob Wick, source

Further Reading

ASCE Committee on America’s Infrastructure. 2017. Infrastructure in California. ASCE: Reston, Virginia. https://

Benke, A.C. 1990. A perspective on North America’s vanishing streams. Journal of the North American Benthological Society 9: 77-88.

Börk, K.S., J.F., Krovoza, J.V. Katz and P.B. Moyle. 2012. The rebirth of California Fish & Game Code Section 5937: water for fish. UC Davis Law Review 45: 809-913.

Börk, K., and A.L. Rypel. 2020. Improving infrastructure for wildlife. Natural Resources & Environment.

France, J.W., I.A. Alvi, P.A. Dickson, H.T. Falvey, S.J. Rigbey, and J. Trojanowski. 2018. Independent forensic team report Oroville Dam spillway incident. Technical Report.

Garrett, B.L. 2010. Drowned memories: the submerged places of the Winnemem Wintu. Archaeologies 6: 346–371.

Gregory, R., L. Failing, G. Long. T. McDaniels, and D. Ohlson. 2011. Structured Decision Making: A Practical Guide to Environmental Management. Wiley-Blackwell, West Sussex, UK

Grabowski, Z.J., H. Chang, and E.F. Granek. 2018. Fracturing dams, fractured data: Empirical trends and characteristics of existing and removed dams in the United States. River Research and Applications 34: 526-537. 

Grantham, T., and P. Moyle. Flagging problem dams for fish survival. California WaterBlog, October 24, 2014.

Hansen, H.H., E. Forzono, A. Grams, L. Ohlman, C. Ruskamp, M.A. Pegg, and K.L. Pope. 2020. Exit here: strategies for dealing with aging dams and reservoirs. Aquatic Sciences 82.

Helfman, G.S. 2007. Fish conservation: a guide to understanding and restoring global aquatic biodiversity and fishery resources. Island Press, Washington D.C. USA.

Moser, S.C., and J.F. Hart. 2018. Paying it forward: the path toward climate-safe infrastructure in California. A report of the climate-safe infrastructure working group to the California State Legislature. Technical Report.

Null, S.E., J. Medellin-Azuara, A. Escriva, M. Lent, and J. Lund. 2014. Optimizing the  195–215Dammed: Water Supply Losses and Fish Habitat Gains from Dam Removal in California. Journal of Environmental Management 136: 121-131.

Perales, K.M., J. Rowan, and P.B. Moyle. 2015. Evidence of landlocked Chinook Salmon populations in California. North American Journal of Fisheries Management 35:1101–1105.

Poff, N.L., J.D. Allan, M.B. Bain, J.R. Karr, K.L. Prestegaard, B.D. Richter, R.E. Sparks, and J.C. Stromberg. 1997. The natural flow regime. BioScience 47: 769-784.

Quiñones, R.M, T. Grantham, B. N. Harvey, J. D. Kiernan, M. Klasson, A. P. Wintzer and P.B. Moyle. 2015. Dam removal and anadromous salmonid (Oncorhynchus spp.) conservation in California. Reviews in Fish Biology and Fisheries 25: 195–215. 

Rypel, A.L., T.D. Simonson, D.L. Oele, J.D.T Griffin, T.P. Parks, D. Seibel, C.M. Roberts, S. Toshner, L.S. Tate, and J. Lyons. 2019. Flexible classification of Wisconsin lakes for improved fisheries conservation and management. Fisheries 44: 225-238.

US Army Corps of Engineers: Federal Emergency Management Agency. National Inventory of Dams. 2018. Washington, DC USA


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Whiplash Again! – Learning from Wet (and Dry) Years

by Jay Lund, Deirdre Des Jardins, Kathy Schaefer

Tulare Lake in July 1983 and May 2023

“Old superlatives have been dusted off and new ones count to better describe the tragedy, damage, and trauma associated with the State’s latest ‘unusual’ weather experience.” DWR Bulletin 69-83, California High Water 1982-83, p.1

“California’s climate has often been described as variable, inconsistent, and unpredictable. The meteorological events of the last few years give additional credence to those observations. The two extremes of weather patterns the record back-to-back dry years of 1976-77 and the all-time record of consecutive wet water years, 1981-82 and 1982-83 — have now been recorded in less than a single decade!” DWR Bulletin 69-83, California High Water 1982-83, p.1

In July 1984, the California Department of Water Resources issued Bulletin 69-83, California High Water 1982-83.  It insightfully reviewed what is still California’s wettest water year in more than a century.  Reading this report gives a sense of California’s broad and eternal flood vulnerabilities and management problems.  Despite important advances since that time, many similar ideas could be written today.

Here are a few long-term lessons from the 1983 and 2023 experiences:

  1. California often has wet and very wet years, just as it often has dry and very dry years.
  2. Flooding can occur in all parts of California, and many parts can flood in the same year.  Few areas should feel entirely safe from floods. Flood hazard zones should be updated to consider subsidence, land use changes and climate change.
  3. Floods have many causes, including regional flooding from major rivers, local tributaries, very local storm drainage, coastal storm driven waves, and infrastructure failures.  All cases can cause sizable property damage and deaths.
  4. Effective infrastructure really helps.  For major river flooding, California’s systems of flood bypasses, levees, and reservoirs were highly effective, but will have vulnerabilities for extreme wet conditions which are becoming more likely with greater climate variability. Flood-fighting by local and state agencies greatly improve levee reliability, but local levee breaks must be expected and prepared for in a system with thousands of miles of levees.
  5. Warnings and evacuations greatly reduce deaths from flooding, but reducing property damages requires investments and regulations to reduce flooding and flood vulnerabilities.  Most deaths are from people traveling through flood waters (often by car) and local levee failures. 
  6. The Flood Operation Center was a beehive of activity this winter, as it was in 1983. The co-located activities of the Department of Water Resources and the National Weather collaboration are a valuable service to the State. Sharing resources, expertise, and technology has been an excellent investment.
  7. This year’s emergency conditions in the Tulare Lake basin also occurred in 1983 and disrupted agricultural production in the region for two years.  (DWR 1984, p. 73)
  8. Agency postmortems for major events are vital to improve understanding of present and future problems.  However, public agency documents usually find it easier to recount the history of events, losses, and successes, than to identify specifically and broadly causes of failures. Identifying systemic improvements must usually occur outside these documents, but is vitally important.  It is important to systematically reflect on, discuss, and learn from the experiences of each extreme event, wet or dry (Pinter et al. 2019).  Postmortem reports from major extreme events are opportunities to improve the understanding and functioning of California’s water system and should be expected and discussed to facilitate improvements.

This year (2023) we were lucky enough to have a cool spring to slow snowmelt.  In 1983, “There was, of course, a little bit of luck: Recall the termination of the rainfall and the unseasonably cool temperatures during the peak of the snowmelt period in the southern Sierra Nevada, which moderated the melt and possibly averted disastrous flooding in the San Joaquin Valley.” (p.4).  Luck always helps, but we should not count on it. 

Floods require serious long-term organization and preparation for past and still larger extremes.  Prepare with diligence and humility, for preparation is never perfect.  “There is no question that the various entities involved achieved some degree of success in managing the 1982-83 flood fight. We must realize that, although man’s ability to manage the extremes of the elements is sometimes successful, Nature bats last!” p. 4

Let’s hope that old agency postmortems and reflections can again be made available conveniently on the web to help us reflect on present and coming challenges.  These are helpful for understanding and restoring faith and pride in government, and perhaps more important for fostering the kinds of conversations we need professionally and publicly.

California has seen incredible floods and flooding in the past and must prepare for major flood events in the future.  Floods and droughts are inevitable in California, just as hurricanes are inevitable on the US Eastern seaboard and tornadoes are inevitable in the Midwest.  In all these cases, loss of life and economic damages are greatly reduced by preparation, infrastructure, warnings, and analytically-informed discussions and decisions.

Be prepared. 

Jay Lund is a Professor of Civil and Environmental Engineering and Vice-Director of the Center for Watershed Sciences at UC Davis.  Deirdre Des Jardins (@flowinguphill) is a tenacious researcher and policy advocate on climate adaptation in California water. Kathy Schaefer is a PhD Candidate at the University of California – Davis completing a dissertation on community-based flood insurance.

Further Reading/Listening

A nice panel discussion on Weather Whiplash from May 18, 2023

Bertino, M. (2023), “Tulare Lake Basin Flooding: An update for early May,” Bountiful Ag blog, May 12, 2023

California Department of Water Resources (1984), California High Water 1982-83, Bulletin 69-83, July. [Alas, State agencies no longer maintain historical documents on their public websites.]

California Department of Water Resources (2022), Central Valley Flood Protection Plan, Update 2022.

Department of Water Resources (DWR) (1978), The 1976-1977 California Drought – A Review, California Department of Water Resources, Sacramento, CA, 239 pp. [Alas, State agencies no longer maintain historical documents on their public websites.]

California Department of Water Resources (2021) California’s Drought of 2012–2016: An Overview..

Lund, J.R. (2012), “Flood Management in California,” Water, Vol. 4, pp. 157-169; doi:10.3390/w4010157.

Pinter, N., J. Lund, and P. Moyle. “The California Water Model: Resilience through Failure,” Hydrological Processes, Vol. 22, Iss. 12, pp. 1775-1779, 2019.

Swain DL, Langenbrunner B, Neelin JD, Hall A. (2018) Increasing precipitation volatility in twenty-first-century California. Nature Clim Change. 8(5):427–433. doi:10.1038/s41558-018-0140-y.

Tulare County Master Flood Control Plan (1971),

Note: Apparently Twitter is no longer automatically announcing blog posts from WordPress, from this or any other blogs. So I recommend that if you like a post, please pass it on by Twitter, Mastadon, LinkedIn, etc. (The biggest sources of disruption are often people and institutions.)

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Monster Fish: Lessons for Sturgeon Management in California

West Coast and California Sturgeon once reached massive sizes. Photos depict large white sturgeon captured from (left, 1500 lbs) Snake River, OR and (right, 468 lbs) California. Sturgeon these sizes are no longer observed in California. Photo credits: Vancouver Island University and the San Bernardino Country Sun.

By Peter B. Moyle & Andrew L. Rypel

If you ever watched National Geographic television and are interested fishes and rivers, you likely have some familiarity with Dr. Zeb Hogan. He hosted a series of shows on giant freshwater fishes, called Monster Fish. He and a colleague also recently published a fascinating book (Hogan and Lovgren 2023) on global adventures searching for giant freshwater fishes. This book is likely to interest California Water Blog readers for several reasons.

Zeb Hogan and a juvenile cultured lake sturgeon, which was being released into the Tennessee River as part of a restoration program.  Photo: Tennessee Aquarium.
  • Zeb obtained a PhD in Ecology from UC Davis working with Bernie May, Peter Moyle, and other faculty. His dissertation included a study of the biology and conservation of giant catfish in the Mekong River, documenting it was close to extinction.
  • His new book discusses sturgeon conservation at length and provides additional background useful for saving the white and green sturgeon in California.
  • The book is an entertaining travelogue featuring trips to rivers around the globe to answer the question: What is the biggest freshwater fish? It also features a strong conservation message, showing why “megafishes” are so important for aquatic conservation.
  • It calls attention to the Mekong River in particular, an amazingly diverse and threatened ecosystem. The Mekong supports 500 endemic fish species and its fisheries feed millions of people. Giant catfish, carp (barbs) and sting rays are part of the river’s fish native fauna. Mekong fish and fisheries are especially threatened by hydropower dams (Hogan et al. 2004). Some scientists are convinced that such dams can be built and operated in ways that don’t affect fish populations, a proposition we are skeptical of, given our experience with California dams and fish.

Zeb confined his megafish search to species that spend their entire lives in freshwater. If he had included fishes that occur in freshwater but spend much of their lives in saltwater, the search would be short. He did not consider these fishes because going out to sea or into an estuary gives fish access to marine resources that allow them to grow rapidly to large size. This is the primary reason salmon and steelhead go out to sea. If anadromous fish were included, sturgeon would win the big fish contest, fins down!  Number 1 would be Beluga sturgeon from Russia, which have been recorded as long as 8 m in length and 1.4 tons. Number 2 would be white sturgeon from the west coast North America, which have been recorded as long as 6.7 m long and 800 kg (1764 lbs).  

This book recognizes and discusses how sturgeon species across the globe face many shared problems. This is important for California, because there are likely to be common solutions for our problems from other sturgeon populations. Many sturgeons have been reasonably well-studied from their value as caviar producers, as commercial and ‘game’ or ‘sport’ fishes, and as ancient survivors of the mass extinction at the end of the Cretaceous period. Of course, all this has not kept sturgeon from facing extinction recently. There are 27 known sturgeon species/ESUs globally; all of them are rated as in danger of extinction by the International Union for the Conservation of Nature (IUCN). And while the threat to white and green sturgeon has historically been rated as low, this assessment is changing rapidly. In California, factors such as the recent red tide die-off of white sturgeon in San Francisco Bay is generating broad reevaluation of conservation practices (Schreirer et al. 2023).                     

Here are some megafish lessons for California sturgeon:

  • The Beluga sturgeon, the largest and oldest of sturgeon species, is approaching extinction in the wild due to overharvest because its caviar is the most valuable of all sturgeon caviar. Despite regulations that ban fisheries and international trade in Beluga caviar, poaching continues. The sturgeon is now subject of an intense aquaculture industry which raises Belugas for their caviar; this growing industry assures that Beluga sturgeon will continue to exist, if not in the wild. Yet the mystique surrounding wild Beluga caviar enhances its value and demand, which basically ensures poaching of wild fish will continue. It is now, listed by IUCN as critically endangered and it will likely be extinct in the wild soon. In California, white sturgeon are also increasingly cultured for caviar (and meat), and again, poaching similarly continues. The wild white sturgeon population in California is in decline, but also supports a sport fishery which is increasingly efficient in detecting and harvesting sturgeon. For example, it is fairly simple and relatively inexpensive to buy an efficient fish finder. Using just this tool, one can cruise through known sturgeon areas of the estuary looking for large whites. And because sturgeon don’t move much, they are easily captured using hook and line and simple baits.
  • More importantly, poor water quality is now killing adult white sturgeon, and therefore limiting natural production. For decades the white sturgeon has been held up as a positive example of fisheries management. Now, having white sturgeon may survive in the future solely as a cultured fish now seems likely. The red tide that spread across the San Francisco Estuary late last summer killed an unknown number of white sturgeon, and some green sturgeon. Large red tides, harmful algal blooms and corresponding fish kills are often brought on by intense heat waves (Till et al. 2019; Griffith and Gobbler 2020; Tye et al. 2022). Thus, deterioration of water quality in the estuary is linked almost directly with climate change impacts in California. These events are probably just beginning, suggesting that California’s white sturgeon population is becoming less resilient overall. So conservation strategies for the fishery must change.
Zeb Hogan (middle) and others with a large white sturgeon form the Fraser River. Source:
  • The Fraser River (British Colombia, Canada) supports the largest white sturgeon population in Canada, and a valuable sport fishery. Yet in the early 1990s, there was an unexplained die-off of large sturgeon that prompted reevaluation of the fishery. The conservation response was a major, swift and stakeholder-driven. One early action was a switch to catch-and-release fishing. Once this was established, a volunteer tagging program for anglers was organized. “This was a widely successful program with tens of thousands of sturgeon tagged; it yielded valuable data-rich information about their abundance, movements, and growth. A decade into the program, the decline of the sturgeon had been reversed… (Hogan and Lovgren 2023, p. 83)”. Angler attitudes towards sturgeon have broadly changed. Not too long ago, sturgeon species in many regions were classified as ‘rough fish’ or ‘other fish’ and afforded little to no protection via protective regulations (Rypel et al. 2021). The Fraser River example demonstrates a high potential for recovering the Sacramento River population. And why not engage anglers to to tag and release sturgeon they catch to improve information on the population and fishery, especially if these changes lead to more fish?
  • The Kootenai River is a tributary to the Columbia River, and supports a unique, land-locked population of white sturgeon. Although the Kootenai River once supported a white sturgeon fishery, in recent decades the population has become endangered because of pollution from mines, overharvest, and most importantly, construction of Libby Dam in 1974. The dam changed how sediment was transported in the river and resulted in the only spawning site for the sturgeon to be covered in sand, a substrate that is very poor for early life survival. The sturgeon population persisted for decades without natural reproduction only because of their longevity. To save the fish, the Kootenai Tribe built a sophisticated hatchery on the river and now releases juvenile sturgeon into the habitat to augment the population of the few remaining adults. “A hatchery can buy you time to restore the river, assuming there is the knowledge, money, and political will to do so. But these restoration efforts often fall short, in which case species like the white sturgeon will depend on hatcheries in perpetuity (Hogan and Lovgren 2023, p.85.”). For more discussion of hatcheries see Rypel and Moyle (2023).
(Top) Picture of the now extinct Chinese paddlefish, from Zhang et al. 2020. (Bottom) A Chinese sturgeon, which was injured and rescued earlier, awaits release into the Yangtze river in Shanghai, June 17, 2007. China Daily Information Corp.
  • China has, or had, populations of Chinese sturgeon, Yangtze sturgeon, and Chinese paddlefish, a close sturgeon relative. The Chinese paddlefish was recently declared extinct (Zhang et al. 2020) and the two sturgeon species are extinct or near extinct in the wild, except for those released into the Yangtze River from hatcheries (Zhuang et al. 1997; Zhuang et al. 2016). The root cause of decline for these fishes is the fundamental transformation of the river by a chain of dams (including the Three Gorges Dam, by some measures the largest dam in the world) that eliminated spawning habitat and most other suitable habitat. Extinctions do happen, and this is a possible future for white and green sturgeon in the Sacramento River and estuary if essential conditions for all life history stages are not maintained.
  • The lake sturgeon of eastern North America is also a contender for biggest freshwater fish because it spends its entire life-cycle in lakes and rivers, reaching up to nine feet long (275 pounds) and living at least 150 years. It was once one of the most abundant fish in Lake Erie and other large natural lakes, but it was decimated by unregulated fisheries during the 19th century. Cumulative impacts ultimately left just a tiny fraction of the original population and resulted in the species being listed as ‘endangered’, by IUCN and number of US states. In Wisconsin, the fishery was first banned (1915) but then allowed to resume as a sport fishery under close supervision in 1934 while the life-history and population ecology were better studied, especially in Lake Winnebago and its main tributaries. Over time, biologists collected data on abundance, sex ratios of spawners, and growth changes of fish every spring during the spawning migration. Using these meticulously collected data, it was originally estimated, and ultimately confirmed, that ~5% of the adult population could be sustainably harvested every year; this quota is taken mainly by spearfishing during a short ice season in February. Access to the fishery is tightly restricted via a lottery system. Biologists and anglers also work in tandem with fishers to collect data on all harvested fish. This management system is popular among anglers because the lucky quota winners could potentially catch fish approaching the historic maximum size. For them, it is a once-in-a-lifetime experience. Abundance has, in turn, increased dramatically over time given the excellent management. During spring now, hundreds of large sturgeon move upstream to spawn, an event that attracts many viewers, including local volunteers who go so far as protecting the large fish from poachers at night (a.k.a. ‘sturgeon guards’). This shows the high potential for “what science-driven management, community support, and a long-term commitment to the preservation of a large freshwater fish can accomplish (Hogan and Lovgren 2023, p.214)”.
(Left) Another excellent book (Schmitt Kline et al. 2009) on the biology, management, and culture of Lake Sturgeon in Lake Winnebago, WI. (Right) Wisconsin DNR and USFWS biologists collecting annual data on the size, sex ratio, and age and growth of spawning adults. Photo credit Mark Hoffman/Milwaukee Journal Sentinel:


A major point of the megafish book is that large fish are among the most vulnerable to decline and eventual extinction from human-made causes. Sadly, many of the species Zeb searched for may not be around in the near future unless action is taken to protect them, especially through habitat protection and management. Science and proper monitoring is extremely critical, and we must keep learning about the biology of these interesting animals to understand how to protect them better. For example, we only just realized that there are actually two migration behaviors in California green sturgeon (Colborne et al. 2022; Colborne et al. 2023). Community engagement is also essential – these are fishes that the public is often willing to protect, and will work hard to do so (Schmitt Kline et al. 2009). If their extinction occurs on our watches, it is a stain on all of us. The best hope for “monster fish” is that they are used as flagship species to encourage habitat conservation on a large scale. In California that would be a great role for white and green sturgeon!

So, what is the biggest freshwater fish? You will have read the book to find out. Suffice it to say that your reading trip of discovery will be most enjoyable, despite what you may have concluded from our focus on sturgeon problems. Zeb Hogan and co-author Stefan Lovgren have done a great job of introducing the reader to some of the world’s most interesting fishes, aquatic habitats, and fish people.

Peter B. Moyle is a Distinguished Professor Emeritus at the University of California, Davis and is Associate Director of the Center for Watershed Sciences. Andrew L. Rypel is a professor of Wildlife, Fish & Conservation Biology and Co-Director of the Center for Watershed Sciences at the University of California, Davis.

California white sturgeon that perished as part of the red tide during late summer 2022. Photos from Schreier et al. 2022.

Further Reading

Colborne, S.F., L.W. Sheppard, D.R. O’Donnell, D.C. Reuman, J.A. Walter, G.P. Singer, J.T. Kelly, M.J. Thomas, and A.L. Rypel. 2022. Intraspecific variation in migration timing of green sturgeon in the Sacramento River system. Ecosphere 13: e4139.

Colborne, S.F., L.W. Sheppard, D.R. O’Donnell, D.C. Reuman, J.A. Walter, G.P. Singer, J.T. Kelly, M.J. Thomas, and A.L. Rypel. 2023. Green sturgeon in California: hidden lives revealed from long-term tracking.

Griffith, A. W., and C. J. Gobler. 2020. Harmful algal blooms: A climate change co-stressor in marine and freshwater ecosystems. Harmful Algae 91:101590.

Hogan, Z. and S. Lovgren. 2023. Chasing Giants: In Search of the World’s Largest Freshwater Fish. University of Nevada Press, Reno NV USA.

Hogan, Z. S., P. B. Moyle, B. May, M. J. Vander Zander, and I. G. Baird. 2004. The imperiled giants of the Mekong. American Scientist 92: 228-237.

Rypel, A. L., P. Saffarinia, C. C. Vaughn, L. Nesper, K. O’Reilly, C. A. Parisek, M. L. Miller, P. B. Moyle, N. A. Fangue, and M. Bell‐Tilcock. 2021. Goodbye to “rough fish”: paradigm shift in the conservation of native fishes. Fisheries 46(12):605-616.

Rypel, A.L., and P.B. Moyle. 2023. Hatcheries alone cannot save fish and fisheries.

Schmitt Kline, K., R.M. Bruch, F.P. Binkowski, and B. Rashid. 2009. People of the sturgeon: Wisconsin’s love affair with an ancient fish. Wisconsin Historical Society Press, Chicago IL USA.

Schreier, A., P.B. Moyle, N.J. Demetras, S. Baird, D. Cocherell, N.A. Fangue, K. Sellheim, J. Walter, M. Johnston, S. Colborne, L.S. Lewis, and A.L. Rypel. 2022. White sturgeon: is an ancient survivor facing extinction in California?

Till, A., A. L. Rypel, A. Bray, and S. B. Fey. 2019. Fish die-offs are concurrent with thermal extremes in north temperate lakes. Nature Climate Change 9(8):637-641.

Tye, S. P., A. M. Siepielski, A. Bray, A. L. Rypel, N. B. Phelps, and S. B. Fey. 2022. Climate warming amplifies the frequency of fish mass mortality events across north temperate lakes. Limnology and Oceanography Letters 7(6):510-519.

Zhang, H., I. Jarić, D. L. Roberts, Y. He, H. Du, J. Wu, C. Wang, and Q. Wei. 2020. Extinction of one of the world’s largest freshwater fishes: Lessons for conserving the endangered Yangtze fauna. Science of the Total Environment 710:136242.

Zhuang, P., F. e. Ke, Q. Wei, X. He, and Y. Cen. 1997. Biology and life history of Dabry’s sturgeon, Acipenser dabryanus, in the Yangtze River. Environmental Biology of Fishes 48:257-264.

Zhuang, P., F. Zhao, T. Zhang, Y. Chen, J. Liu, L. Zhang, and B. Kynard. 2016. New evidence may support the persistence and adaptability of the near-extinct Chinese sturgeon. Biological Conservation 193:66-69.

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