by Robert Lusardi, Peter Moyle, Patrick Samuel, and Jacob Katz
California is a hot spot for endemic species, those found nowhere else in the world. Among these species are 20 kinds of salmon and trout. That is an astonishing number considering California is also literally a hot-spot in terms of summer temperatures and that these salmonids are cold-water adapted. These 20 endemic are joined by 12 other species with broader distributions, north along the Pacific Coast. In California, native salmon and trout are at the southern end of the range. They survive here because mountains intercept rain and snow in the cooler months of the year and the powerful California Current keeps the ocean and coast cool year-round. The big question is: can California’s diverse salmon and trout continue to persist in the face of a warming climate and declining coldwater resources?
We think the answer to this question is yes. But first, the bad news. A new report issued by the Center for Watershed Sciences and California Trout has found that nearly 75% of the state’s salmon and trout (salmonids) could be extinct within the next 100 years. Nearly 45% could meet the same fate in just 50 years if present trends continue. The good news is that the report shows that most of these fishes can continue to persist if appropriate actions are taken.
The report, State of the Salmonids II: Fish in Hot Water, was officially released on May 16th. Originally conceived as an update on a report published in 2008, this report contains new information on how to maintain resilient populations. The report explores three important questions: 1) what is the status of all California salmonids, both individually and collectively, 2) what are the major factors responsible for their present status, and 3) how can California’s salmonids be saved from extinction? To answer these questions, we conducted a thorough literature review and interviewed more than 70 species experts from fishery management agencies over a 14-month period. Based on this research and interviews, the authors generated a full scientific account for each species. Each account was then peer reviewed by at least one, and often two or more, species experts.
We evaluated the status and future of each species using a standard set of seven criteria: (a) area occupied, (b) estimated adult abundance, (c) degree of dependence on human intervention to keep the species going, (d) physiological tolerance to changing conditions, (e) genetic risks, (f) vulnerability to climate change, and (g) threats from other factors, such as dams and diversions (each factor was evaluated separately to produce a composite score). Each of the seven criteria was scored on a scale of 1 to 5, with 1 indicating the most extreme threat. The scores were then averaged to produce an overall score, rating the ‘level of concern’ for each species (Table 1). The scoring indicated 14 species were of critical concern, with a high risk of extinction in the wild, nine were of high concern, seven of moderate concern, and one of low concern (Figure 1). One species, bull trout, is already extinct in California.
Looking at this another way, 71% of anadromous salmon and trout and 74% of inland trout in California scored as critical or high concern, indicating a high likelihood of extinction in the next 100 years. Further, 25 taxa are worse off than they were in 2008. Downward changes in status were attributed to a continued decline from multiple factors, an improved scoring system, and the recent historic drought. Species most likely to disappear from California included coho salmon, chum salmon, pink salmon, Sacramento winter-run Chinook salmon, two distinct populations of spring-run Chinook salmon, two distinct populations of summer steelhead, steelhead of the south coast, California golden trout, Kern River rainbow trout, and McCloud River redband trout.
The good news is that 31 of 32 salmonids are still present in California. This speaks to their ability to persist during difficult periods. In fact, salmonids have been able to persevere for more than 50 million years despite volcanic eruptions, earthquakes, mega-droughts, and other climatic extremes. Their ability to make it through these events is a reflection of the evolutionary enriched behavioral and life history diversity among populations and species. Behavioral and life history diversity contribute to population and species resiliency under changing conditions. When times are challenging, some populations die off while others hang on, ensuring long-term species persistence.
Over the last century, however, the ability of most of these salmonids to adapt to changing conditions has been greatly reduced due to rapid and extreme habitat degradation and interactions of hatchery salmonids with wild salmonids. As a result, salmonids are more vulnerable to changing conditions today than ever before. This is particularly alarming considering that our analysis found that climate change was a critical or high threat for 84% of all salmonids in California, making it the single largest threat. Climate change is affecting streamflow and temperature, reducing habitat, shifting food webs, and changing interactions between native and nonnative fishes.
The State of the Salmonids II report makes it clear that many native salmonids in California are on a trajectory towards extinction, if present trends continue. The report outlines a set of solutions, termed “return to resilience,” the central tenet of which is improving behavioral and life history diversity of salmonid species. The general strategy can be broken into two sets of actions: managing places and conceptual strategies. Within “places,” we recommend focusing on protecting and/or restoring four important types of habitats throughout California. These include the following, which are not mutually exclusive:
1) Stronghold Watersheds, or the remaining fully functioning aquatic ecosystems in California such as the Smith River, Blue Creek, and the Eel River, so that they may continue to protect and enhance salmonid diversity,
2) Source Waters such as mountain meadows, springs, and groundwater, which will be vitally important in buffering the effects of climate change and providing cold water during the late summer and drought, and
3) Productive and Diverse Habitats including floodplains, lagoons, coastal estuaries, and spring-fed rivers—these are some of the most productive aquatic systems in California which have been shown to increase salmonid growth rates, alter migration timing and life history diversity, and improve adult returns.
4) Endemic Trout Waters. These are the isolated waters scattered around the state that are important for species like Eagle Lake Trout, California golden trout, and McCloud River redband trout. If the waters are altered significantly, the factors that make the endemic species unique will be lost. Good examples, in progress, include restoring streams that support Goose Lake redband trout, restoring Pine Creek (the principal spawning stream for Eagle Lake rainbow trout), or enhancing flows in streams that support southern steelhead.
The report also discusses three important, conceptually based strategies to enhance salmonid diversity and production.
The first strategy is to embrace reconciliation ecology as a management tool. Most ecosystems in California are altered by human actions with people continuing to be a key part of the ecosystem. If the mechanisms supporting enhanced salmon and steelhead growth and diversity can be replicated in working landscapes, then this concept should be embraced. A good example of this is the Yolo Bypass in the Central Valley where rice fields are being used as surrogate floodplain habitat and have been shown to greatly enhance growth in juvenile salmonids.
We also recommend improving habitat connectivity and passage to historical spawning and rearing habitat. In general, improving connectivity among habitats used by different life stages of salmon and trout is desirable, as is renewed connectivity to historical spawning and rearing habitats. Restoring connectivity of main rivers to their floodplains is one example of this. This also includes providing volitional passage over dams or removing dams that are no longer economically viable. Access to historical spawning and rearing habitat may enhance population diversity and resilience to change.
The final concept for managing coldwater fishes is genetic management. The genetic effects of hatchery salmonids on wild fish are numerous and well documented. Broad changes in genetic management and a reduction in interactions between hatchery and wild fish is required and is of fundamental importance. At a minimum, such changes include the need to reduce gene flow between hatchery and wild salmonids, minimize straying of hatchery fish into adjacent watersheds, and marking all hatchery fish so that they can be distinguished from wild fish.
These “return to resilience” strategies are not limited by geography or taxonomic boundaries. Rather, the actions should to be applied broadly throughout California if we want to have these iconic fish around for future generations of Californians. The challenges in improving salmonid behavioral and life history diversity are not easy and require collective will. We are optimistic that positive change is imminent and that if the solutions are fully implemented, many of the species reviewed in the State of the Salmonids II report will thrive in the future.
Robert A. Lusardi is a researcher at the Center for Watershed Sciences and is the California Trout-UC Davis Coldwater Fish Scientist. Peter Moyle is a UC Davis Professor Emeritus of fish biology and an associate director of the Center for Watershed Sciences. Patrick Samuel is the Conservation Program Coordinator for California Trout. Jacob Katz is a Senior Scientist at California Trout.