By Peter Moyle and Tom Taylor

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The fresh waters of California support a diverse native fish fauna, 130 taxa by our count (Leidy and Moyle 2021). At least 56 of these taxa are on trajectories towards extinction 7 are already extinct; 32 are listed as threatened or endangered by state and federal agencies. Not surprisingly, the declining species attract lots of attention because protecting them affects water use statewide. In this blog series, however, we discuss native fishes that are not considered to be in trouble. Instead we discuss native species that have sufficient resiliency in life history, distribution, and physiology to keep populations large and sustainable, even in highly altered habitats. Information on these species should help us to understand why they have such resiliency in the face of large-scale changes to California waterways that have endangered other fishes. We base our discussion on publications such as Moyle (2002), Moyle et al. (2015), and Leidy and Moyle (2021).

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Sacramento sucker in Today’s World

The first species we discuss in this series is the Sacramento Sucker (Catostomus occidentalis). It is among the first of California’s endemic fishes to be described by C.O. Ayres in 1854, using fish he obtained from a San Francisco fish market. Early workers found it to be abundant and widely distributed in virtually all streams, sloughs, and lakes in Sacramento-San Joaquin watershed (Evermann and Clark 1931), as well as in many coastal watersheds. It is abundant in fresh and brackish waters from Goose Lake in the north to the Kern River in the south and has been carried by canals to reservoirs in southern and coastal California. It co-occurs naturally with Golden Trout in streams of the southern Sierra Nevada and with Steelhead and Chinook salmon in the large rivers of the Central Valley. They occupy both cold and warm-water habitats. 

The Sacramento Sucker is one of ten species of sucker (family Catostomidae) found in California. Most are readily recognized by the fleshy papillose lips on their downward pointing mouth. This special attribute allows suckers to feed on benthic food resources while maintaining their body orientation into strong currents. Their body is near-cylindrical and muscular with a long and strong anal fin helps keep their head in contact with the substrate. This combination of traits enables them to live in diverse habitats, where they suck up detritus, algae and small invertebrates from diverse substrates.

The wide distribution and abundance of Sacramento suckers in freshwater habitats meant that they were an important food for native peoples; they could be harvested year-around but were especially accessible in winter and spring when spawning concentrated adults in large numbers in shallow riffles. Fertilized eggs from these spawning events produce clouds of tiny larvae which can be an important item in the diet of juvenile Chinook Salmon that are headed out to sea.

Adult suckers are also important prey for bald eagles, osprey, and river otters in shallow riffles and otters can take them even in deeper habitats. Other interactions we have observed include rainbow trout hovering close behind spawning adult suckers and rushing in to eat the spawn. Suckers are omnivorous and are frequently observed grazing on algae-covered rocks in shallow riffles or on the bottom of deep riverine pools, as well as feeding on pine pollen and newly hatched insect larvae floating on the surface of pools. In short, Sacramento Suckers still are an important component of river ecosystems in California, where they have lots of interactions with other ecosystem members, native and non-native.

Resiliency

Sacramento Suckers are remarkably resilient. This is not surprising given that they evolved in a region where the natural aquatic environment is highly variable, with long droughts and major flood events. The evolutionary history of the suckers has allowed them to persist through the massive changes made to the lands and waters of California by the dominant culture (us). The general view held by EuroAmerican (white) settlers of California has been that most native fishes (except salmon and trout) were “rough fish” that could be easily be replaced by non-native fishes (Rypel et al. 2021). This led to the establishment of about 50 non-native fish species, including Common Carp, Largemouth Bass, American Shad, and Brook Trout, which were all perceived as being superior to the native fishes in the altered habitats of modern day California. These attitudes are changing. For example, the Pomo Tribe in northern California has strived to maintain their cultural connection with suckers by refurbishing rock wier fish traps associated with springs of cold water that flow into Big Lake on the Fall River. The suckers can be harvested in mid-winter during their spawning runs. 

Sacramento Suckers have managed to live in altered habitats with non-native fishes, especially in reservoirs. Historically, state and federal fish and water agencies regarded the Sacramento Sucker as a prime example of an unwanted species that was thriving in the large reservoirs built in the twentieth century as well as in the cold ‘tail waters’ of rivers below these dams. When we arrived on the scene in the 1970s, the favored method of dealing with the ‘rough fish problem’ was to apply large quantities of fish poisons to rivers, operations that were euphemistically called “chemical treatments.” While all native non-salmonid fishes were targeted, the eradication of sucker populations was usually the main objective because suckers often made up a high percentagever of the fish biomass and were therefore thought to depress populations of more favored fish, especially rainabow trout (Moyle et al. 1983). In 1977, we, with two van-loads of students, observed an attempt by CDFG to poison out fishes in the North Fork Feather River. We observed hundreds of dying fish and measured and weighed many of them (8 species), which gave us data about the size and age composition of the populations in the poisoned sections.

The results demonstrated the impressive resilience of Sacramento Suckers (and other native fishes). Two sections of the river were poisoned. The first was right below a dam and had not been poisoned in years prior to this attempt. The second section was immediately below the first one and had been poisoned 11 years earlier. The suckers in the first section had a size (length) and age distribution that would characterize a self-sustaining-population, with lots juvenile suckers of multiple age classes and modest numbers of adult fish that were 5-10 years old. The second section was dominated by adult suckers that were 6-8 years old and fairly uniform in size. Apparently a few suckers in the second section had survived the poisoning and had successfully spawned the following year, leaving behind fish of just one strong year class. The large cohort of uniform-sized suckers presumably suppressed spawning of following cohorts through competition for food or even predation, but it also showed how suckers responded to disturbance; a few individuals could recreate the population. Other life history traits also improved long term persistence, such as high fecundity, a physiological tolerance of a wide range of conditions, large adult size (up to 50 cm FL) and life span, and other adaptations (Moyle 2002). 

This pattern shows that the suckers have a life history that has allowed them to persist through natural disasters, for thousands of years. The poisoning mimicked natural disaster (e.g., severe drought or fire) for which the suckers were pre-adapted. When healthy habitat conditions return, suckers are often the first native fish to re-establish populations. This happened in Putah Creek, the stream that runs through Davis. When sufficient flows returned to the creek following a minimum flow agreement in 2000, suckers spawned successfully in multiple years. 

Conclusions

The Sacramento Sucker is a remarkable species that is endemic to northern California waters. It has persisted despite rapid environmental change and remains an important player in river ecosystems, as bottom-feeding omnivores, even in rivers that are dominated by non-native fishes. We have both spent time snorkeling Central Valley rivers, watching groups of suckers graze, using their ‘fleshy papillose lips’ to suck up invertebrates , algae and detritus from the substrate while their long anal fins keep them in contact with the bottom. We have also been attracted to the splashing of aggregations of suckers vigorously spawning in shallow riffles. We appreciate the connection such events make to times past when native fishes were all thriving. Increasingly, anglers even enjoy the challenge of catching (and releasing) suckers with light tackle.

About the Authors

Peter Moyle is Distinguished Professor Emeritus at the University of California, Davis and is Associate Director of the Center for Watershed Sciences.

Tom Taylor has had a long career as an agency and consulting biologist, often working with native fishes. He has also taken underwater photos of many of the fishes, which will illustrate the blogs.

Further Reading

Ayres, W. O. 1854. Catostomus occidentalis Ayres. Proceedings of the California Academy of Natural Sciences 1:18–19. https://www.biodiversitylibrary.org/page/15967057

Baltz, D. M. and P.B. Moyle. 1984. Segregation by species and size classes of rainbow trout, Salmo gairdneri and Sacramento sucker, Catostomus occidentalis in three California streams. Environmental Biology of Fishes 10:101-110. https://doi.org/10.1007/BF00001666

Evermann, B. W., & Clark, H. W. 1931. A Distributional List of the Species of Freshwater Fishes Known to Occur in California. Fish Bulletin 35. Sacramento: California State Printing Office, California Division of Fish and Game. 67 pp.

Leidy R.L. and P.B. Moyle 2021. Keeping up with the status of freshwater fishes: a California (USA) perspective. Conservation Science and Practice 3(8), e474. https://doi.org/10.1111/csp2.474. 10 pages.

Moyle, P. B. 2002. Inland Fishes of California. Revised and Expanded. Berkeley: University of California Press. 502 pp. https://www.ucpress.edu/book/9780520227545/inland-fishes-of-California. 

Moyle, P.B. 2021. Living with non-native fishes in California requires using the right words. California WaterBlog. https://californiawaterblog.com/2021/08/08/living-with-non-native-fishes-in-california-requires-using-the-right-words

Moyle, P.B. 2023.Future Ancestors of Freshwater Fishes in California. California WaterBlog. https://californiawaterblog.com/2023/09/17/future-ancestors-of-freshwater-fishes-in-california

Moyle, P.B. and M.A. Campbell. 2023. DNA Unveils New Freshwater Fish Species in California. California WaterBlog. https://californiawaterblog.com/2023/01/29/dna-unveils-new-freshwater-fish-species-in-California%20

Moyle, P.B. and R.L. Leidy. 2023. Freshwater fishes: threatened species and threatened waters on a global scale. Pages 177-206 In N. Maclean, editor. The Living Planet: The Present State of the World’s Wildlife. Cambridge University Press.

Moyle, P.B., R. M. Quiñones, J.V.E. Katz, and J. Weaver. 2015. Fish Species of Special Concern in California. 3rd edition. 842 pp. Sacramento: California Department of Fish and Wildlife. https://www.wildlife.ca.gov/Conservation/Fishes/Special-Concern

Moyle, P.B., B. Vondracek, and G. D. Grossman. 1983. Responses of fish populations in the North Fork of the Feather River, California, to treatments with fish toxicants. North American Journal of Fisheries Management 3:48-60. https://doi.org/10.1577/1548-8659(1983)3%3C48:ROFPIT%3E2.0.CO;2

Rypel, A.L., Saffarinia, P., Vaughn, C.C., Nesper, L., O’Reilly, K., Parisek, C.A., Miller, M.L., Moyle, P.B., Fangue, N.A., Bell‐Tilcock, M. and Ayers, D., 2021. Goodbye to “rough fish”: paradigm shift in the conservation of native fishes. Fisheries 46(12): 605-616. https://doi.org/10.1002/fsh.10660T

Taylor, T.L. and D. G. Price. 1982. Fishes of the Clear Lake Basin. Pages 172-223. In P. B. Moyle (Editor), Distribution and Ecology of Stream Fishes of the Sacramento-San Joaquin Drainage System, California. UC Publications in Zoology 115, University of California Press, Berkeley, California.