By Jacob Katz and Peter Moyle
In the previous blog, Jay Lund argued that wide-scale, integrated management of California’s water system will better balance water needs of the environment and water demands by humans. Here we expand on the need for fundamental shifts in policy to recover populations of Central Valley salmon using integrated management approaches.
The Central Valley is the only place on Earth with four distinct runs of Chinook salmon (fall, late-fall, winter, and spring). Each run was adapted for different conditions and had multiple independent populations that spawned in different valley tributaries. Historically, this “diversified portfolio” included 1-2 million spawning fish per year in Central Valley rivers (Yoshiyama et al. 1998). In 2009, total returns for all four runs were just over 70,000 fish, around 5% of average historical abundance. Today, the winter and spring runs are listed under the Endangered Species Act (in 1990 and 1998, respectively), and the late-fall run is small and in decline. In recent decades most salmon returning to the Central Valley have been fall-run fish, primarily of hatchery origin (AFRP 2011). The decline of California’s wild fall-run Chinook salmon populations has been both obscured and exacerbated by massive hatchery production.
Although they may look similar to wild fish, hatchery salmon are, in a very real sense, domestic animals. Hatcheries cultivate domestic genes, resulting in salmon adapted to hatchery conditions but unfit for survival in the wild under all but the most favorable conditions (Araki et al. 2007, 2008, Kostow 2009, Christie et al. 2012). Currently more than 30 million Chinook smolts are released annually from Central Valley hatcheries irrespective of the return rate of hatchery fish. As a result, hatchery production is at an all-time high while wild spawners and fisheries yields are at an all-time low.
Those few hatchery fish that do return to the valley often do not return to the hatchery where they were born, but rather stray, spawning in rivers instead. Although most spawning by strays is unsuccessful, these strays interfere with the spawning of the few, if any, wild fish remaining (Johnson et al. 2012). This is a particularly important point because a wild salmon produces, on average, eight times more grandchildren than does a hatchery fish (Chilcote et al. 2011).
The past 60 years of Central Valley hatchery production to support fisheries has resulted in replacement of multiple natural populations with one hatchery population, thereby greatly increasing extinction risk (Williamson and May 2005, Williams 2006, Barnet-Johnson et al. 2007, Lindley et al. 2009, CDFG unpublished coded wire wag data 2011, Katz et al. 2012, Johnson et al. 2012). The situation is similar to managing financial investments for long-term yields, where a well-diversified investment portfolio (i.e., multiple runs with multiple independent populations) will fluctuate less in response to volatile market conditions (i.e., environmental variation) than will one concentrated in just one or two stocks (i.e., just hatchery fish). Today, the management portfolio of Central Valley salmon is overwhelmingly concentrated in hatchery production. This all-eggs-in-one-basket strategy is an underlying cause of the recent collapse of salmon numbers (Lindley et al. 2009). Recovery of self-sustaining runs of Central Valley salmon will be impossible if we do not stop interbreeding between hatchery and naturally spawning populations (Katz et al. 2012). Actions to support separating hatchery and wild gene pools can be sorted into two broad categories:
Physical Segregation: Move hatcheries from upstream areas, where they are currently, to the bottom of the watersheds, in or close to the estuaries. This action would increase the smolt to adult survival rates by eliminating high mortality of hatchery fish in rivers and the Delta (from the more than 30 million hatchery smolts released, only 29,000 adults returned in 2009, that is less than 0.1%) while minimizing competition between wild and natural fish and limiting genetic dilution of wild gene pools.
Mark all hatchery fish with both adipose fin clips and internal tags so that all hatchery fish can be visually distinguished and management can effectively minimize interbreeding.
Genetic Segregation: Hatchery propagation meant to subsidize fisheries should use stocks for breeding that are as genetically divergent from native salmon as possible. Broodstock should be selected for life-history characters (especially migratory timing) incompatible with California hydrology. This action would minimize genetic dilution of wild gene pools because hybrid progeny will be unfit for local conditions and therefore unlikely to survive to produce progeny of their own.
Because of the fragmented nature of the current system of salmon management, we spend tens of millions of dollars annually to produce salmon in inland hatcheries, and then spend hundreds of millions more to deal with the environmental, regulatory and legal consequences of having produced those same fish. As was suggested for water management in the previous blog, this piecemeal approach to fisheries resource management is not economically viable. Nor is this strategy viable for avoiding extinction. Accordingly, a comprehensive re-thinking of hatchery management must be undertaken in California and where adverse impacts to natural spawning populations outweigh benefits, hatcheries should be closed.
Jacob Katz is a doctoral student in fish ecology and Peter Moyle is a professor of fish biology at the UC Davis Center for Watershed Sciences.
Anadromous Fish Restoration Program (AFRP) of the United States Fish and Wildlife Service, Stockton, California. http://www.fws.gov/stockton/afrp/ accessed Feb 1 2011.
Araki, H., B. A. Berejikian, M. J. Ford, and M. S. Blouin. 2008. Fitness of hatchery reared salmonids in the wild. Evolutionary Applications 1:342-355.
Araki, H., B. Cooper, and M. S. Blouin. 2007. Genetic effects of captive breeding cause a rapid, cumulative fitness decline in the wild. Science 318:100-103.
Barnett-Johnson, R., C. B. Grimes, C. F. Royer, and C. J. Donohoe. 2007. Identifying the contribution of wild and hatchery Chinook salmon (Oncorhynchus tshawytscha) to the ocean fishery using otolith microstructure as natural tags. Canadian Journal of Fisheries and Aquatic Sciences 64:1683-1692.
Chilcote, M. W., K. W. Goodson, and M. R. Falcy. 2011. Reduced recruitment performance in natural populations of anadromous salmonids associated with hatchery-reared fish. Canadian Journal of Fisheries and Aquatic Sciences 68:511-522.
Christie, M. R., M. L. Marine, R. A. French, and M. S. Blouin. 2012. Genetic adaptation to captivity can occur in a single generation. Proceedings of the National Academy of Sciences 109:238-242.
Johnson, R. C., P. K. Weber, J. D. Wikert, M. L. Workman, R. B. MacFarlane, M. J. Grove, and A. K. Schmitt. 2012. Managed metapopulations: Do salmon hatchery sources lead to in-river sinks in Conservation? PloS ONE 7:e28880.
Katz, J, P. B. Moyle, R. M. Quiñones, J. Israel, and S. Purdy. 2012. Impending extinction of salmon, steelhead, and trout (Salmonidae) in California. Environmental Biology of Fishes. DOI 10.1007/s10641-012-9974-8
Kostow, K. 2009. Factors that contribute to the ecological risks of salmon and steelhead hatchery programs and some mitigating strategies. Reviews in Fish Biology and Fisheries 19:9-31.
Lindley, S. T., C. B. Grimes, M. S. Mohr, W. T. Peterson, J. E. Stein, J. J. Anderson, L. W. Botsford, D. L. Bottom, C. A. Busack, and T. K. Collier. 2009. What caused the Sacramento River fall Chinook stock collapse? US Dept. of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southwest Fisheries Science Center, Fisheries Ecology Division.
Moyle, P.B., J.A. Israel, and S. E. Purdy. 2008. Salmon, steelhead, and trout in California: status of an emblematic fauna. UC Davis Center for Watershed Sciences. 316 pp. (http://watershed.ucdavis.edu/pdf/SOS-Californias-Native-Fish-Crisis-Final-Report.pdf)
Williams, J. G. 2006. Central Valley Salmon: A perspective on Chinook and Steelhead in the Central Valley of California. San Francisco Estuary and Watershed Science 4.
Williamson, K. S. and B. May. 2005. Homogenization of fall-run Chinook salmon gene pools in the Central Valley of California, USA. North American Journal of Fisheries Management 25:993-1009.
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.