By Lynette Williams Duman & Mason Rogers
The forgotten panfish of the West
Bluegill, redear sunfish, and largemouth bass: these species are familiar and, for many, elicit fond memories of fishing in warm waters on a hot summer’s day. It is for this reason, and others, that California has introduced these sportfishes, and a myriad of other non-native fishes, into the Sacramento-San Joaquin Delta (Delta) since the 1870s. UC Davis Distinguished Professor Peter Moyle states that “the dissatisfaction of early settlers with the native fishes [of California]” motivated these early introductions (Moyle 1976). Unfamiliar to anglers settling in California from the East, the native fishes of California’s Central Valley have historically failed to draw sport anglers, with one exception – the Sacramento perch (Archoplites interruptus) (Figure 1). However, despite its once-desirable status, it no longer finds itself part of the California sportfishing conversation. They are entirely extirpated from their native range. However, they have avoided total extinction because native fish enthusiasts and anglers intentionally introduced them to non-conventional waterways across the west.
So what happened to the perch?
The Sacramento perch is unique. It is the only member of the family Centrarchidae (the fish family containing many of our most beloved sportfishes, such as black basses, crappies, and sunfishes) native to waters west of the Rocky Mountains. Like its eastern cousins, it is a piscivorous predator – that is, it eats fish – which makes it a great sportfish. Once highly abundant in California’s Central Valley, Salinas and Pajaro Rivers, and Clear Lake, it is now absent from its native waters.
What happened?
California’s waterways are highly altered by extensive wetland loss, water diversions, land use changes, and non-native species introductions (Brown 2003, Nichols et al 1986). The leading causes for the extirpation of the Sacramento perch can be distilled down to habitat destruction, embryo predation from non-native species, and interspecific competition for food and space with non-natives. The perch had mostly disappeared from their native range by the 1950s, and due to continued alterations to geography and hydrology, conditions remain generally unfavorable for their reintroduction (Moyle 2002, Moyle and Williams 1990).
Widespread habitat restoration within the contiguous Delta is unlikely to re-create Sacramento perch habitat – abiotic conditions within the greater watershed, species introductions, and waterway alterations create habitats so altered from their historic state that they probably wouldn’t support the perch, and restoration can’t reverse all of these changes. The extirpation of the Sacramento perch from its native range does not bode well for its continued existence, but they have been spared from extinction. They have been widely introduced to water bodies throughout the western states for angling opportunities, mostly by enthusiasts (Figure 2).
Sacramento perch, like many native species, are adapted to a wide range of conditions due to California’s hydrologic variability. Their high tolerance for alkaline conditions and wide temperature swings makes perch an ideal candidate for stocking in places from high altitude, cold reservoirs and lakes to the backyard and stock ponds that most non-native sportfishes cannot tolerate (Moyle 2002, Crain and Moyle 2011). Even though Sacramento perch can survive in small bodies of water, their populations are most robust in cold, high-altitude bodies of water such as Pyramid Lake, Lake Crowley, and Bridgeport Reservoir.
Despite stocking efforts in many different water bodies, Sacramento perch still face threats. Small, isolated populations are susceptible to crashes because of lack of gene flow and inbreeding. Some of the small water bodies they now call home dry up during persistent droughts, such as Jewel Lake in Contra Costa County. Others experience dramatic (sometimes fatal) swings in water quality, like prolonged declines in dissolved oxygen (East Bay Times 2015). In addition to water quality metrics, non-native species, particularly bluegill, have been shown to outcompete Sacramento perch in controlled settings and could play a non-negligible role in limiting their populations (Marchetti 1999). Continued persistence of these populations depends on sporadic transfers of fish between isolated water bodies (Crain and Moyle 2011). The variability associated with isolated waterbodies, non-native species assemblages, and the precarious position of these populations is why continuous monitoring is critical, but this has not been a high management priority until recently.
Ironically, the widespread introduction of Sacramento perch outside of native waters is the reason that they are not listed as an endangered species, which creates a double-edged sword for their conservation. On the one hand, this limits public investment in their survival, but it also allows scientists to have the flexibility to attempt unconventional conservation methods without the endangered species permitting hurdles (Moyle 2002).
Sacramento perch in the modern world
Most of the “perch ponds” where the fish persist are not typical native fish habitat, and they have historically been written off as unimportant for species conservation. As a result, the status of many Sacramento perch populations is unknown. The Aquatic Research Collective (ARC) at the UC Davis Center for Watershed Sciences, as well as the Native Fishes Unit at the California Department of Fish and Wildlife, have reignited efforts to monitor, assess, and increase populations of Sacramento perch in these manmade and often unconventional waters. ARC biologist Mason Rogers leads “Pursuing the Establishment of Reconciliatory Centrarchid Habitat” or “PERCH” Project, where the main objective is to revisit historic “perch ponds” in the Davis-vicinity, assessing:
1. Whether Sacramento perch populations still exist in these sparsely monitored ponds (Figure 3);
2. Whether water quality conditions and pre-existing fish community assemblage are suitable for Sacramento perch populations to persist indefinitely; and seeking to
3. Inform future introduction efforts and set a precedence for monitoring populations.
This work has been catalyzed by support from the Department of Water Resources (DWR). With DWR’s support, the PERCH Project is comparing historic ponds with an experimental population in the Dutch Slough tidal restoration project, to understand what conditions may support new perch introductions elsewhere (DWR 2024).
So, one native sunfish does well in ponds. What’s the big deal?
This research will set the stage for future Sacramento perch introductions, both by documenting existing populations for use as genetic source stock and to provide the science to support introductions.
Native fishes throughout California are doing poorly. Freshwater systems, despite being less than 1% of the Earth’s surface, contain 43% of all fish species, so conservation of these systems is critical for combatting biodiversity loss (Grosberg et al 2012, Cochran-Biederman et al 2014).
Freshwater systems in California are mostly controlled and used by humans, with water diversions the key determinant of native fish decline, followed by non-native species introductions (Moyle and Williams 1990, Miller et al 1989). Restoration of conditions in which those species evolved is often difficult or impossible. Moreover, the viability of planting native freshwater species into native ranges is difficult to assess because failures often are not published (Cochran-Biederman et al 2014). That’s what makes Sacramento perch so interesting and potentially important for native fish restoration. The Sacramento perch avoided extinction through “assisted migration” to more suitable waters once its own home range was irreparably altered.
Because Sacramento perch persist in novel, man-made habitats, such as stock ponds, backyard fishing ponds, reservoirs, and stormwater basins, they offer a story of hope in an era that desperately needs it. These efforts may offer a path forward for some listed species; for Delta smelt (Hypomesus transpacificus), a species that is federally endangered, a similar form of “assisted migration” to high altitude reservoirs may provide favorable conditions for this largely freshwater pelagic fish that has been virtually extirpated from the modern Delta (Stompe et al 2021).
The lesson here is that man-made water infrastructure, such as reservoirs, ponds, culverts, and canals can provide habitat for native species at risk, even if the modified areas have not been historically considered native fish habitat. In an era when ecosystem-wide change is sometimes irreversible, conservation should be geared towards reconciliation rather than returning to unattainable historic conditions. Thinking outside the box on conventional conservation is key (Hobbs et al 2009). Sacramento perch could very well chart a course for native fish conservation in the 21st century. Opportunities for species conservation exist both in old and new habitats, and existing habitats can be reconsidered to accommodate new understandings about global change and habitat alteration.
The next steps for Sacramento perch are daunting but exhilarating: how do we rekindle a societal value for them in angling and how do we get them into more waterways for everyone to enjoy?
Lynette Williams Duman is a PhD student in the Aquatic Research Collective at the UC Davis Center for Watershed Sciences. Mason Rogers is a staff biologist at the Aquatic Research Collective at the UC Davis Center for Watershed Sciences.
Further Reading
Moyle, P. B., & Williams, J. E. (1990). Biodiversity loss in the temperate zone: decline of the native fish fauna of California. Conservation Biology, 4(3), 275-284.
Moyle, P. B. (2002). Inland fishes of California: revised and expanded. Univ of California Press.
Moyle, P. B. (1976). Fish introductions in California: history and impact on native fishes. Biological Conservation, 9(2), 101-118.
Nichols, F. H., Cloern, J. E., Luoma, S. N., & Peterson, D. H. (1986). The modification of an estuary. Science, 231(4738), 567-573.
Brown, L. R. (2003). A summary of the San Francisco tidal wetlands restoration series. San Francisco Estuary and Watershed Science, 1(1).
Crain, P. K., & Moyle, P. B. (2011). Biology, history, status and conservation of Sacramento perch, Archoplites interruptus. San Francisco Estuary and Watershed Science, 9(1).
Cochran‐Biederman, J. L., Wyman, K. E., French, W. E., & Loppnow, G. L. (2015). Identifying correlates of success and failure of native freshwater fish reintroductions. Conservation Biology, 29(1), 175-186.
United States Fish and Wildlife Service. (2023). Sacramento Perch Featuring Peter Moyle and Max Fish. Fish of the Week Podcast. February 6.
Hobbs, R. J., Higgs, E., & Harris, J. A. (2009). Novel ecosystems: implications for conservation and restoration. Trends in ecology & evolution, 24(11), 599-605.
Miller, R. R., Williams, J. D., & Williams, J. E. (1989). Extinctions of North American fishes during the past century. Fisheries, 14(6), 22-38.
Grosberg, R. K., Vermeij, G. J., & Wainwright, P. C. (2012). Biodiversity in water and on land. Current Biology, 22(21), R900-R903.
Stompe, D. K., O’Rear, T. A., Durand, J.R., Moyle, P.B. (2021). Home is where the habitat is. California Waterblog. July 4. https://californiawaterblog.com/2021/07/04/home-is-where-the-habitat-is/
Bay Area News Group. (2015). Tilden’s Jewel Lake Reduced to a Puddle. East Bay Times. September 14. https://www.eastbaytimes.com/2015/09/14/tildens-jewel-lake-reduced-to-a-puddle/
Marchetti, M. P. (1999). An experimental study of competition between the native Sacramento perch (Archoplites interruptus) and introduced bluegill (Lepomis macrochirus). Biological invasions, 1, 55-65.
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