Hatcheries and enhancement

Hatcheries have a specific purpose: to produce free-range salmon. But hatchery salmon depend on money, fuel and government support every single year. As government spending becomes tighter, these runs will fail.

Hatchery salmon are at greatest risk from disease. Disease spreads more rapidly in captivity because there are more fish and less water than in the wild. Disease mutates more easily in captivity because the predators are not allowed the contagious diseased fish. Disease becomes more virulent in captivity because there is no risk in killing its host, there will always be another fish to infect. As salmon farms increase parasites, bacteria and viruses, free salmon are bringing new and more disease into the rivers.

Crowding them is becoming increasingly dangerous whether in the sluggish flow of spawning channels or minimal flow in hatcheries. Spawning channels that are left to fill with debris and carcasses are death traps to wild salmon. Communities have to take responsibility to maintain or close them.


Research found a negative relationship between the reproductive performance in natural, anadromous populations of steelhead trout (Oncorhynchus mykiss), coho salmon (O. kisutch), and Chinook salmon (O. tshawytscha), and the proportion of hatchery fish in the spawning population. The effect of hatchery fish on reproductive performance was the same among all three species. In most cases, measures that minimize the interactions between wild and hatchery fish will be the best long-term conservation strategy for wild populations.

Previous research suggests hatchery-reared fish may be less fit than wild fish under natural spawning and stream-rearing conditions. In this study, measures of population productivity were used to indirectly examine the possibility of differential reproductive success between wild and hatchery fish in 12 populations of steelhead. For natural populations, removal rather than addition of hatchery fish may be the most effective strategy to improve productivity and resilience.

The common management practice of introducing artificially produced fish into wild populations has raised concerns among fishery biologists. In this review, Einum and Fleming show that the hatchery rearing of salmonids results in increased pre-adult aggression, decreased response to predators, and decreased survival. Based on the presented evidence they conclude that differences between hatchery-reared and wild fish may have negative implications for the success of stocking programs.

Authors evaluate the Salmonid Enhancement Program (SEP) to determine its effectiveness at producing adult fish in the catch and its ability to learn from experience. Overall, the program has fallen short of its objectives: SEP has devoted considerable effort in evaluating individual facilities and sites, however, the program has been unable or unwilling to evaluate overall program success and direction. Furthermore, there is a paucity of information on wild stocks and the extent to which these enhancement activities have an effect on their numbers.

Maintaining viable populations of salmon in the wild is a primary goal for many conservation and recovery programs. The frequency and extent of connectivity among natal sources defines the demographic and genetic boundaries of a population. Yet, the role that immigration of hatchery-produced adults may play in altering population dynamics and fitness of natural populations remains largely unquantified. Quantifying, whether natural populations are self-sustaining, functions as sources (population growth rate in the absence of dispersal), or as sinks can be obscured by an inability to identify immigrants. In this study researchers use a new isotopic approach to demonstrate that a natural spawning population of Chinook salmon, (Oncorhynchus tshawytscha) considered relatively healthy, represents a sink population when the contribution of hatchery immigrants is taken into consideration. When population growth rate of the natural population was modeled to account for the contribution of previously unidentified hatchery immigrants, hatchery-produced fish caused the false appearance of positive population growth. These findings highlight the potential dangers in ignoring source-sink dynamics in recovering natural populations, and question the extent to which declines in natural salmon populations are undetected by monitoring programs.

Artificial culture of salmonids may relax the selective pressures from predators, thereby altering behavioral and heart rate responses to predation risk and imposing new selection that adapts fish to confinement. This research suggests domestication selection may alter reaction norms of cultured animals over environmental gradients and time. This should be considered when attempting to predict the consequences of release or escape of domesticated animals in the wild.

Salmonid management based largely on hatchery production, with no overt and large-scale ecosystem-level recovery program, is doomed to failure. Not only does it fail to address the real causes of salmonid decline, but it may actually exacerbate the problem and accelerate the extinction process.

State and federal agencies in the United States annually release millions of hatchery salmon and steelhead into public waters. These hatchery programs pose genetic and ecological risks to wild fish populations. This paper reviews some of the factors that contribute to ecological risks, including the relative abundance of hatchery and wild fish in natural production areas, hatchery programs that increase density-dependant mortality, residual hatchery fish, some physical advantages that hatchery fish can have over wild fish, and life history characteristics that may make some species especially vulnerable to the effects of ecological risks. This paper provides mitigation strategies to help manage the risks posed by interactions between hatchery and wild fish.

Authors investigated concerns of potential impacts of high levels of escapees in the North Atlantic from Atlantic salmon farms on native salmon populations. Experimental results indicate reduced survival in farm and cross-bred salmon compared to wild stocks, as well as displacement of wild parr by faster growing hybrid juveniles. Where suitable habitat for emigrant parr was absent, this competition would result in reduced wild smolt production. Results demonstrated We thus that interaction of farm with wild salmon results in lowered fitness, with repeated escapes causing cumulative fitness depression and potentially an extinction vortex in vulnerable populations.

A central feature of recovery efforts to declining wild salmon stocks has been to build many hatcheries to produce large quantities of fish to restock streams. This approach addresses the symptoms but not the causes of the declines (an example of a halfway technology), because the habitats remain largely unsuitable for salmon. The author recommends that salmonid management turn from the symptoms to the causes of decline, including overharvest and habitat destruction.

Adverse ecological effects on wild fish resulting from releases of hatchery-reared fish are increasingly being scrutinized and balanced against benefits afforded by hatchery programs. In this chapter, authors provide insight into the potential for adverse impacts resulting from ecological interactions between hatchery and wild fish, and also put forward factors that could mitigate or minimize those ecological interactions.

Conservation hatcheries are unproven in restoring threatened and endangered populations of salmon to sustainable levels, and may cause more harm than good. Nonetheless, a recent court decision found that the National Marine Fisheries Service (NMFS) must include hatchery salmon in Endangered Species Act listings, where NMFS has included those fish as components of the core “evolutionarily significant units (ESUs).” This undercuts efforts for restoration of wild salmon. Hatcheries generally reduce current fitness and inhibit future adaptation of natural populations. Hence, the legal definition of an ESU must be unambiguous and must exclude hatchery fish.

To aid in the recovery of depressed wild salmon populations, the operation of hatcheries must be changed to reduce interactions of juvenile hatchery fish with wild fish. Evidence suggests that productivity of wild populations can be reduced by the presence of large numbers of hatchery smolts in lower rivers and estuaries that attract predators. Alterations to hatchery programs that could encourage recovery of wild populations include (i) avoiding release of large numbers of smolts in areas with high concentrations of wild fish, (ii) decreasing the number of smolts released, and (iii) using a volitional release strategy or a strategy that employs smaller release groups spread temporally.

Deleterious genetic change in wild anadromous salmonids (Oncorhynchus spp.) is expected from fisheries differentially harvesting fish that spawn at particular times within a season, mature at particular sizes or ages, or grow at particular rates. Other sources include overfishing, habitat degradation or destruction, and interactions with hatchery fish, particularly when these phenomena severely reduce population size. Gene flow from hatchery to wild fish populations also is deleterious because hatchery populations genetically adapt to the unnatural conditions of the hatchery environment at the expense of adaptation for living in natural streams. One suggested action is to establish or maintain refuge populations of wild fish that are to be protected from habitat degradation, selective or intense fishing, and introductions with hatchery fish.

For more links relating to the issues of domestication, ecological competition, fitness, genetic introgression, strays, supplementation and survival in hatchery and wild salmonids, please see the science library of the Wild Fish Conservancy.