The effects of massive quantities of hatchery-raised salmon on native populations are only now becoming clear, and on the California Water Blog, Dr. Peter Moyle and Jakob Katz write about the insanity of California’s fragmented salmon & water management:
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.
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).
California’s hatchery system costs tens of millions to operate, yet it may be costing the state far more in terms of its effects on salmon populations.
Moyle and Katz call for a systemwide evaluation of hatchery programs, and suggest a pair of strategies which would lessen the impacts of hatchery fish on wild salmon populations:
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.
With all that’s been learned recently about how unsuited most hatchery fish are to life in the wild (and their far lower reproductive rates), it’s clear that hatchery systems aren’t a mitigation for many salmon problems — they’re often a part of the problem itself.