Scientific Evidence on Adverse Effects of Steelhead Hatcheries
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- Effects of domestication: Hatchery production is a form of species domestication in which individuals adapt to the regime of genetic selection for a life cycle that includes spawning, egg hatching, and juvenile rearing in a protected, human-controlled environment. Traditional hatchery stocks (such as Chambers Creek steelhead) that are developed in order to provide fish for harvest become highly domesticated as they are selected by hatchery managers to fulfill this role. This makes them highly unfit for a life cycle spent entirely in the wild. Recently, hatchery broodstocks have been developed from local wild populations for conservation purposes to “supplement” wild spawning populations. However, these fish also experience domestication selection to the hatchery environment that reduces their fitness to reproduce naturally compared to their wild counterparts. Relative to wild fish, hatchery fish produce fewer returning adults when they spawn with one another, or when one supplementation hatchery fish spawns with a wild fish. This ultimately alters the genetics of the lineage (even within a single generation of captivity) and reduces reproductive success in the wild (Christie et al. 2011). Consequently, at best, this kind of “conservation” hatchery practice has only limited value as a conservation tool and should be used for very short periods of time (no longer than 10 years) to avoid damaging effects of domestication; strict monitoring is required.
- Reduced fitness of hatchery steelhead: As a result of their domestication, hatchery produced steelhead are not adapted to selective pressures of the natural environment. Furthermore, they lack the genetic adaptation to the spawning grounds on which their reproductive success in the wild depends. Not surprisingly, hatchery steelhead have vastly inferior rates of survival and reproductive success (McLean et al. 2003; Quinn 2005; Chilcote et al. 2011).
- Risks of introgression: Despite significantly reduced survival rates, the few hatchery steelhead that manage to survive to adulthood may “stray” onto the spawning grounds of native fish and spawn with wild steelhead. The inferior genetics (which generate traits and behaviors that are sub-optimal for survival and reproduction in the wild) are then passed on to the new generation of the wild population. As the genes of domesticated hatchery fish enter the wild population, the overall fitness and reproductive capacity of the wild stock — fine-tuned from millions of years of evolution — is reduced and may be forever lost. Using the dog analogy: your retriever is lucky enough to survive in the wild long enough to mate with a wolf. Their offspring will be unsuccessful, as the retriever genes in the pups are poorly suited for life in the wild. It is in this way that hatchery fish can drag down the success of wild fish populations.
- Demonstrated effects of hatcheries on wild population reproductive success: No matter the methodology utilized by the hatchery or the length of time that local wild populations are exposed to interactions with hatchery fish within a watershed, there is a negative correlation between the reproductive performance of the total wild population and the proportion of hatchery steelhead in the spawning population (Chilcote et al. 2011). Therefore, long-term conservation of a population depends on the “minimization” of hatchery-wild interactions. In any specific case, “minimization” must be clearly specified. Additionally, there must be a method to accurately measure the effects of interaction in quantitative terms. If interactions between hatchery and wild fish cannot be accurately measured, elimination of the conservation risk is the best mode of action. Most likely, eliminating the risk of hatchery-wild interactions is necessary in most cases.
- Competition for limited resources and the concept of density dependence: Within a given watershed, there is a limited amount of food resources and habitats suitable to provide shelter from predators and water currents (which partially determine metabolic rates). If resources are abundant or there is little competition from other fish, all steelhead within a river or stream should be able to find feeding territories, ample food resources, and shelter; these fish will have high probabilities of survival in freshwater and at sea due to the size advantage gained from greater feeding opportunities. However, if resources and suitable habitats become limited and the number of rearing juveniles too great, there will be competition for the food and shelter that is available. As a result, all fish within the community will not be able to survive and reach critical size requirements for survival at sea. As the population of the community is curbed by competition for available resources and shelter, “carrying capacity” is reached in which the size of the fish population for a given area inhibits the population’s potential for growth (density dependence). While density dependence occurs mainly within freshwater environments, it has also been demonstrated to a lesser degree in the open ocean (Quinn 2005).
- Effects of hatchery production on wild steelhead populations: When hatchery fish are suddenly released into watersheds containing rearing wild steelhead populations, the number of salmonids for a given area and resource supply becomes too great for the system. As a result, the carrying capacity of the region is breached and competition for a fixed amount of resources limits the survival of smaller and less aggressive fish. Hatchery fish that have been released into the wild are generally larger and more aggressive for a given age class than wild steelhead (Nakano 1994; Gotceitas and Godin 1992; Berejikian et al. 1996). Once hatchery fish enter the ecosystem they often outcompete and displace wild steelhead which possess greater potential for survival at sea and reproduction at the spawning grounds (Berejikian et al. 1996; McMichael et al. 1999).
- Adult competition for limited spawning territories: When steelhead have fully matured at sea, they will return to natal spawning grounds in search of ideal territories to dig their redds, spawn, and protect fertilized eggs. Water conditions, flows, and gravel size determine optimal grounds for survival of offspring. As a result, there is a limited capacity for successful reproduction in a given watershed. Competition will arise for optimal spawning grounds and fertilization of females. While hatchery-produced fish demonstrate greatly inferior reproductive capacity and survival, the few that are able to survive and escape the fishery may compete with wild fish on the spawning grounds. This is an additional harm that may limit the success of threatened or endangered wild populations. It is important to recognize that hatchery fish do not have to be successful spawners in the wild to have this impact on wild fish; annual hatchery releases ensure a steady population of stray hatchery fish each year. Unlike the wild fish, the stray hatchery fish pay no fitness cost for their poor reproductive performance and continually impose this competitive burden on wild fish on the spawning grounds.
- Demonstrated effects of hatcheries on wild population reproductive success: Under all hatchery scenarios, the more hatchery steelhead present within the spawning population, the poorer the productivity of the total population (Chilcote et al. 2011). While the exact mechanisms for this result have not fully been determined, they are likely a combination of both ecological competition and genetics. For example, McLean et al (2003) demonstrated that Chambers Creek steelhead spawning with one another in the wild (Forks Creek, Willapa Bay) produced only 5 to 10 % the number of returning adults as wild Forks Creek steelhead spawning among themselves.
- Food resources of juvenile salmonids: Rearing juvenile steelhead feed primarily on drifting insects and crustacean zooplankton; however, as they grow, steelhead become more capable of feeding on various fish species including salmonids (Quinn 2005). Salmonids are capable of consuming fish greater than 40% of their body length (Pearsons and Fritts 1999). Hatchery fish will compete with wild fish for limited food resources within a stream reach.
- Predation of wild steelhead by hatchery-origin fish: Artificial feeding conditions of hatchery facilities produce salmonids of greater sizes than wild freshwater rearing steelhead. When hatchery salmonids are released into a watershed, they often feed on smaller wild steelhead that hold greater potential for survival at sea and reproductive success (Naman 2008). Some large hatchery steelhead smolts may in fact fail to migrate to the ocean altogether; these “residualized” resident fish prey on small rearing juvenile steelhead and salmon throughout all life stages. As a result, hatchery propagation diminishes the success of wild steelhead populations.
- Enhancement of predation on wild steelhead from hatchery releases and predator attraction: In addition to predation from hatchery origin salmonids, large quantities of hatchery fish within a stream attract greater abundances of non-salmonid predators. Hatchery fish are not subjected to predator-related selection pressures within the hatchery facility. When thousands of hatchery fish overwhelm a watershed reach and display risky behaviors, predators are attracted resulting in greater predation of residing wild steelhead (Johnsson et al. 2001; Nickelson 2003).
- Increased risk from disease: Wild fish can be exposed to greater numbers of pathogens from both released hatchery fish and the effluent discharged from a steelhead hatchery. The density of fish found in a hatchery is far beyond that found in the wild, creating conditions conducive to disease outbreaks, which can in turn affect wild populations (NOAA 2011).
Steelhead hatcheries also cause adverse effects on wild populations through 1) facility effects (e.g., water use, effluent discharge, fish passage blockages); 2) fish removal (e.g., collection, delaying migration, displaced spawning); 3) harvest (the recreational and commercial pursuit of hatchery steelhead stocks leads to pressure on wild steelhead, even in “catch and release recreational fisheries); and 4) monitoring and evaluation programs designed to determine the performance of the hatchery programs. For more information on these effects, see NOAA 2011.
- Raised in closely controlled artificial conditions, hatchery fish fail to be exposed to natural selection pressures at every step of their upbringing. Initially, the hatchery staff determines which males will fertilize the eggs of selected females; only these eggs are incubated and hatched. Once the fry emerge, they are subjected to a period of rapid and unnatural growth in which the fish are fed pellets by humans or by automated feeders. At no point do the juveniles become exposed to selective pressures that would be experienced in the wild; they pay none of the survival costs that maladapted fish in the wild are forced to pay. Instead, the juveniles adapt to a manufactured and protected facility environment. After rapid development in low-risk rearing ponds, the domesticated steelhead are released downstream where they will fend for themselves for the very first time. Downstream, their success is not dissimilar to what you would expect if you released your pet dog to live in the wild.
- It is very unlikely that hatcheries could be used to rebuild a population. Even those few “conservation hatcheries” or “integrated” programs that use local wild fish as their broodstock (see the brief discussion on the Elwha River page) have not demonstrated success. The fish returning as adults are not as productive as the naturally reproducing wild steelhead as “domestication” of the fish occurs in the first generation. These programs also require continual “mining” of the local population for broodstock. For the most part, these programs have been unsuccessful, and a 2013 WDFW assessment recommends they be discontinued in the Lower Columbia.