DIFFERENCES BETWEEN HATCHERY AND WILD SALMONIDS
BASED ON THE SCIENTIFIC LITERATURE
The following quotes are based on scientific evaluation and most are from peer reviewed scientific papers. The lead author and the date of publication are provided for reference. Hatchery solutions for wild salmonid decline have ignited a debate about their effectiveness and impact on wild, native salmonids. While science has shown that in many cases hatchery programs are in conflict with wild salmonid conservation and recovery, the ongoing problem is that this information is not being effectively applied by the management agencies.
Allendorf et al. 1994: We are not aware of a single empirical example in which (hatchery) supplementation has been successfully used as a temporary strategy to permanently increase abundance of naturally spawning populations of Pacific salmon.
Altukhov et al 1991: Artificial reproduction, commercial fisheries, and transfers result in the impairment of gene diversity in salmon populations, and so cause their biological degradation.
Araki et al. 2008: Captive breeding is used to supplement populations of many species that are declining in the wild. The suitability of and long-term species survival from such programs remain largely untested, however. We measured lifetime reproductive success of the first two generations of steelhead trout that were reared in captivity and bred in the wild after they were released. By reconstructing a three-generation pedigree with microsatellite markers, we show that genetic effects of domestication reduce subsequent reproductive capabilities by 40% per captive-reared generation when fish are moved to natural environments. These results suggest that even a few generations of domestication may have negative effects on natural reproduction in the wild and that the repeated use of captive-reared parents to supplement wild populations should be carefully reconsidered.
Araki et al. 2008: “Our review indicates that salmonids appear to be very susceptible to fitness loss while in captivity. The degree of fitness loss appears to be mitigated to some extent by using local, wild fish for broodstock, but we found little evidence to suggest that it can be avoided altogether. The general finding of low relative fitness of hatchery fish combined with studies that have found broad scale negative associations between the presence of hatchery fish and wild population performance, should give fisheries managers pause as they consider whether to include hatchery production in their conservation toolbox.”
Bachman 1984: Hatchery brown trout fed less, moved more, and expended more energy than wild brown trout in streams.
Bams 1970: Hatchery pink salmon migrated to the ocean one to two weeks earlier than wild pinks.
Berejikian and Ford 2003: Competitive asymmetries between hatchery and natural spawners and possibly their offspring can clearly contribute to the differences in relative fitness. Hatchery fish have lower fitness.
Blouin 2003: Non-local domesticated hatchery summer-run steelhead achieved 17-54% the lifetime fitness of natural native fish.
Blouin 2009: "If anyone ever had any doubts about the genetic differences between hatchery and wild fish, the data are now pretty clear. The effect is so strong that it carries over into the first wild-born generation. Even if fish are born in the wild and survive to reproduce, those adults that had hatchery parents still produce substantially fewer surviving offspring than those with wild parents. That's pretty remarkable."
Blouin 2009: “The implication is that hatchery salmonids – many of which do survive to reproduce in the wild– could be gradually reducing the fitness of the wild populations with which they interbreed. Those hatchery fish provide one more hurdle to overcome in the goal of sustaining wild runs, along with problems caused by dams, loss or degradation of habitat, pollution, overfishing and other causes. Aside from weakening the wild gene pool, the release of captive-bred fish also raises the risk of introducing diseases and increasing competition for limited resources.”
Blouin 2009: There is about a 40% loss in reproductive fitness for each generation spent in a hatchery.
Brannon et al. 1999: (Independent Scientific Advisory Board) : The three recent independent reviews of fish and wildlife recovery efforts in the Columbia River Basin addressed hatcheries. There was consensus among the three panels (National Fish Hatchery Review Panel, National Research Council, Independent Science Group), which underscores the importance of their contributions in revising the scientific foundation for hatchery policy. The ten general conclusions made by the panels are listed below.
1. Hatcheries generally have failed to meet their objectives
2. Hatcheries have imparted adverse effects on natural populations
3. Managers have failed to evaluate hatchery programs
4. Rationale justifying hatchery production was based on untested assumptions.
5. Hatchery supplementation should be linked with habitat improvements
6. Genetic considerations have to be included in hatchery programs.
7. More research and experimental approaches are required.
8. Stock transfers and introductions of non-native species should be discontinued.
9. Artificial production should have a new role in fisheries management.
10. Hatcheries should be used as temporary refuges rather than for long-term production.
Brauner 1994: In freshwater swimming velocity tests, wild coho salmon smolts swam faster than hatchery fish. In seawater hatchery fish performance compared to wild fish was poor. Hatchery fish had more difficulty osmoregulating.
Byrne et al. 1992: Building more hatcheries should cause alarm to biologists concerned with the preservation of native stocks until it is demonstrated that supplementation can be done in a way that does not reduce fitness of the native stock.
California Dept. Fish and Game 2002: The brains of hatchery raised rainbow trout are smaller in 7 out of 8 critical neuroanatomical measures than those of their wild reared counterparts.
Chilcote et al. 1986: Hatchery steelhead are only 38% as successful in producing smolts as wild steelhead.
Chilcote 2002: “…there will be little benefit to bringing some of the wild fish into the hatchery environment if the resulting hatchery smolts will have ocean survival rates that are 1/10 of those for wild smolts….all indications are that hatchery fish, even from wild broodstocks, are not as successful as wild fish in producing viable offspring under natural conditions….”
Chilcote 2003: A naturally spawning population comprised of equal numbers of hatchery and wild fish would produce 63% fewer recruits per spawner than one comprised entirely of wild fish. For natural populations, removal rather than addition of hatchery fish may be the most effective strategy to improve productivity and resilience.
Chilcote 2008: At a recent meeting of lower Columbia River Salmon Recovery Stakeholders, the document , Recovery Strategies to Close the Conservation Gap Methods and Assumptions, hatchery fish impacts are discussed. It says, “…relative population survival rates (recruits produced per spawner) were found to decrease at a rate equal to or greater than the proportion of hatchery fish in the natural spawning population. In other words, a spawning population with 20% hatchery strays (regardless of the type of hatchery program and whether they are integrated or segregated) had the net survival rate (recruits per spawner) that was 20% less than a population comprised entirely of wild fish (0% hatchery strays). Likewise, a population with 40% hatchery strays had a population survival rate that was 40% lower than a population comprised entirely of wild fish.”
Dickson 1982: Juvenile hatchery fish show a behavioral shift in stream feeding position compared to wild fish. Hatchery fish feed nearer the surface. This may expose them to greater predation.
Ersbak et al. 1983: Hatchery trout conditions declined after stocking. Hatchery fish were less flexible in switching to available food in the stream.
Fenderson, 1968: Hatchery fish are more aggressive and dominate wild fish, and hatchery fish have a higher mortality.
Flagg et al., 1999: The reviews conclude that artificial culture environments condition salmonids to respond to food, habitat, conspecifics and predators differently than fish reared in natural environments. It is now recognized that artificial rearing conditions can produce fish distinctly different from wild cohorts in behavior, morphology, and physiology
Fleming, et al., 1993: The divergence of hatchery fish in traits important for reproductive success has raised concerns. This study shows that hatchery coho salmon males are competitively inferior to wild fish, and attained only 62% of the breeding success of wild males. Hatchery females had more difficulty in spawning than wild fish and hatchery fish had only 82% of the breeding success of wild fish. These results indicate hatchery fish may pose an ecological and genetic threat to wild fish.
Fleming et al. 1994: Results of this study imply that hatchery fish have restricted abilities to rehabilitate wild populations, and may pose ecological and genetic threats to the conservation of wild populations.
Fleming et al. 1997: Reproductive success defined in the study as the ability to produce viable eyed embryos did not differ between hatchery and natural females. Hatchery males, however, achieved only 51% the estimated relative reproductive success of natural males under conditions of mutual competition. Hatchery males were less able to monopolize access to spawning females and suffered more severe wounding and greater mortality than natural males.
Flick, et al. 1964: Wild brook trout had higher summer and winter survival than hatchery fish.
Ford, 2002: Substantial phenotypic changes and fitness reductions can occur even if a large fraction of the captive broodstock is brought in from the wild every generation. This suggests that regularly bringing wild-origin broodstock into captive populations cannot be relied upon to eliminate the effects of inadvertent domestication selection.
Gudjonsson and Scarnecchia 2009: “In some rivers the salmon stocks have been enhanced by the release of smolts produced by using local brood stock. Smolts reared in hatcheries and released in rivers frequently had 50% lower return rates than wild smolts.
Hilborn 1992: Pacific salmon hatcheries have failed to deliver expected benefits and they pose the greatest single threat to the long-term maintenance of salmonids.
Hooton 2009: “Most hatchery programs produce steelhead that reflect only a small fraction of the natural life history variability inherent within and between wild populations. The numbers of steelhead that can result from carefully administered hatchery programs may be impressive, but those fish represent only a narrow segment of the diversity and adaptability of wild fish. Such products cannot be relied on to sustain natural populations over the long term.”
Hulett et al. 1994: Hatchery winter steelhead were about one-half as effective as wild winter-run steelhead in naturally producing smolt offspring. Hatchery winter steelhead were about one sixth as effective as wild winter steelhead in naturally produced adult offspring.
IEAB 2002: Cost to catch for hatchery fish:
Hatchery Species Produced Cost of a Salmon that is caught
Leavenworth spring chinook $4,800
Entiat spring chinook $68,031 (Highest $891,000)
Winthrop spring chinook $23,068
Priest Rapids fall chinook $12.00 (Highest - $293)
Irrigon summer steelhead $453
Spring Cr. fall chinook $237 (range 14.53 - $460)
Clatsop coho $124
Spring chinook $233
Fall chinook $65
Nez Perce fall and spring chinook $3,700
McCall spring chinook $786 (range $522 to $1,051)
The benefit of the fishery is $45 to $77 per fish for the commercial fishery and $60 per fish for the sport fishery.
Jonsson et al. 1993: Differences were evident for hatchery Atlantic salmon relative to wild salmon, with common genetic backgrounds, in breeding success after a single generation in the hatchery. Hatchery females averaged about 80% the breeding success of wild females. Hatchery males had significantly reduced breeding success, averaging about 65% of the success of wild males.
Kincaid, 1994: Atlantic salmon held in hatcheries for four generations produced juveniles that had different performance characteristics than progeny from wild parents.
Knudson et al. 2006. “Perhaps the most important conclusion of our study is that even a hatchery program designed to minimize differences between hatchery and wild fish did not produce fish that were identical to wild fish.”
Kostow 2003 : Our data support a conclusion that hatchery summer steelhead adults and their offspring contribute to wild steelhead population declines through competition for spawning and rearing habitats.
Kostow 2004: “In conclusion, this study demonstrated large average phenotype and survival differences between hatchery-produced and naturally produced fish from the same parent gene pool. These results indicate that a different selection regime was affecting each of the groups. The processes indicated by these results can be expected to lead to eventual genetic divergence between the new hatchery stock and its wild source population, thus limiting the usefulness of the stock for conservation purposes to only the first few generations.
Leider, et. al., 1990: The mean percentage of offspring from naturally spawning hatchery steelhead decreased at successive life history stages, compared to wild steelhead, from a potential of 85-87% at the egg stage to 42% at the adult stage. Reproductive success of naturally spawning hatchery steelhead compared to wild steelhead decreases from 75-78% at the subyearling stage to 10.8-12.9% at the adult stage.
Levings, et al., 1986: Hatchery chinook used the estuary a shorter period of time than wild chinook. The greatest overlap between hatchery and wild chinook in the estuary is in the transition zone where greater competition could occur.
Mason, et al., 1997: Hatchery x wild and wild x wild crosses had higher survival in the natural stream compared to hatchery x hatchery crosses.
McClure : “Continued interbreeding with hatchery-origin fish of lower fitness can lower the fitness of the wild population. Generally, large, long-term hatchery programs that dominate production of a population is a high risk factor for certain viability criteria and can lead to increased risk for the population. The populations meeting ‘high viability’ criteria will necessarily be large and spatially complex. In order to meet these criteria (spatial structure and diversity) there should be little or no introgression between hatchery fish and the wild component of the population. Populations supported by hatchery supplementation for more than three generations do not in most cases meet ICTRT viability criteria at the population level.”
McLean et al. 1997: Hatchery steelhead spawning in the wild had markedly lower reproductive success than native wild steelhead. Wild females that spawned in 1996 produced 9 times as many adult offspring per capita as did hatchery females that spawned in the wild. Wild females that spawned in 1997 produced 42 times as many adult offspring as hatchery females. The wild steelhead population more than met replacement requirements (approximately 3.7 – 6.7 adult offspring were produced per female), but the hatchery steelhead were far below replacement (<0.5>
Meffe 1992: Countless salmon stocks have declined precipitously over the last century as a result of overfishing and widespread habitat destruction. A central feature of recovery efforts 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.
Miller, 1953: Hatchery cutthroat trout had lower survival compared to wild fish due to absence of natural selection at early life stages.
Miller et al. 1990: Over 300 (hatchery) supplementation projects were reviewed and the authors found: 1) examples of success at rebuilding self-sustaining anadromous fish runs with hatchery fish are scarce (22 out of 316 projects reviewed), 2) success was primarily from providing fish for harvest, and 3) adverse impacts to wild stocks have been shown or postulated for every type of hatchery fish introduction to rebuild runs.
Moran and Waples 2007: “…we show some compelling differences in reproductive success of hatchery and wild fish. Naturally spawning hatchery fish are less than half as productive as wild fish.”
Mullan, et al., 1992: Hatchery spring chinook produced more precocious males than wild chinook. This could be one factor in the low survival of hatchery fish.
Naish et al. 2008: If one concern has been identified, it is that many hatchery programmes continue to be operated with few objectives, and with a poor understanding of the magnitude and importance of the impacts of genetic effects of hatchery releases and the role of this information in informing remedial actions.
A rapidly growing body of literature points towards detrimental behavioral interactions between hatchery and wild fish. More is known about these interactions in freshwater rearing habitats than in estuarine and marine environments. There is also, however, a paucity of information on whether risk avoidance measures are effective at reducing competition and predation and, as far as we know, little attention is directed towards carrying capacity when the size of release is considered.
Nickelson 1986: Hatchery coho salmon have lower survival than wild coho relative to poor ocean productivity cycles. Hatchery coho juveniles are more abundant after stocking in streams but the result is fewer adult returns and fewer juvenile coho salmon in the next generation than in streams that were not stocked.
Nickelson 2003: 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.
Perry, et al. 1993: Idaho has been trying to unravel the secrets of hatchery and wild salmon interactions in nature. Since hatchery salmon do not survive as well as wild salmon, it is important to fix this problem. It is possible that a hatchery supplementation program may inadvertently replace the target natural population with one having lower survival and reproductive potential.
Ratliff, 1981: Wild fall chinook were more resistant to C. shasta than were hatchery chinook.
Reisenbichler, et al. 1977: His research shows that hatchery x hatchery crosses of steelhead fry survival was lower than for wild x wild crosses and wild x hatchery crosses in streams. Likewise he found that hatchery x hatchery crosses survived better in the hatchery environment. The hatchery fish were derived from local wild steelhead and had changed in performance in two generations of hatchery rearing. Conclusion: differences in survival suggested that the short-term effect of hatchery adults spawning in the wild is the production of fewer smolts and ultimately, fewer returning adults than are produced from the same number of wild steelhead spawners.
Reisenbichler 1986: Most (hatchery fish) outplanting programs have been unsuccessful. Rigorous planning, evaluation, and investigation are required to increase the likelihood of success and the ability to promptly discern failure.
Reisenbichler 1994: Gene flow from hatchery fish also is deleterious because hatchery populations genetically adapt to the unnatural conditions of the hatchery environment at the expense of adaptedness for living in natural streams. This domestication is significant even in the first generation of hatchery rearing.
Reisenbichler 1996: Available data suggest progressively declining fitness for natural rearing with increasing generations in the hatchery. The reduction in survival from egg to adult may be about 25% after one generation in the hatchery and 85% after six generations. Reduction in survival from yearling to adult may be about 15% after one generation in the hatchery and 67% after many generations.
RIST 2009: “Most information available indicates that artificially-propagated fish do have ecological impacts on wild salmonid populations under most conditions (e.g. a 50% reduction in productivity for steelhead in an Oregon population). To the degree that the trait distributions seen in wild salmon populations are adaptations to their environments, selection imposed by the hatchery environment could result in reduced fitness of hatchery fish in the wild.”
Shrimpton, et al., 1994: Juvenile hatchery coho showed a reduced tolerance to salt water compared to wild coho.
Slaney, et al., 1993: Hatchery adult steelhead strayed more than wild steelhead
Sosiak, et al., 1979: As juveniles, hatchery fish had less stomach fullness and fed on fewer taxa than wild fish. This was determined after hatchery fish were in streams from one to three months.
Steward et al. 1990: Authors reviewed 606 hatchery supplementation studies and found that few directly assessed the effects on natural stocks. Genetic and ecological effects and changes in productivity of the native stocks that can result remain largely unmeasured. However, the general failure of supplementation to achieve management objectives is evident from the continued decline of wild stocks.
Swain, et al. 1991: Hatchery coho salmon diverged from the wild fish in fin size and body dimensions. These were considered adaptations to the hatchery environment.
Taylor, 1986: Hatchery coho salmon diverged in body structure and variation from that of the wild coho.
Vincent 1987: Hatchery stocking ended in a Montana stream and wild trout more than doubled (160%) and the wild trout biomass increased by 10 times.
Waples 1991: Genetic interactions between hatchery and wild salmonids will increase as hatchery supplementation becomes a more dominate form of hatchery management.
Waples 1994: Hatchery captive brood stocks may shift genetic structure in natural populations.
Wohlfarth 1986: Stocking with hatchery stocks cannot replace wild productivity because hatchery fish are selected for adaptation to the hatchery environment and do not perform well in the natural environment.
Wood, et al., 1960: Hatchery coho salmon 14 months after release into a stream did not reach the body composition of the wild salmon in time for downstream migration