The road to extinction is paved with good intentions: negative association of fish hatcheries with threatened salmon

Levin, Phillip S.; Zabel, Richard W.; Williams, John G.

doi:10.1098/rspb.2001.1634

Cited by 166 publications

(142 citation statements)

References 23 publications

(32 reference statements)

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“…Production hatcheries release a significant number of unmarked salmon in many regions, therefore there is great interest in understanding whether selective mortality processes in years of poor overall survival bias the population composition towards hatchery-origin fish. Specifically, there is evidence that the presence of hatchery fish reduces the marine survival of naturally spawned individuals, probably due to competition and their larger body size (Levin et al 2001, Ruggerone et al 2010. Conversely, decreased survival rates have also been shown in hatchery fish as a result of asynchronous release timing with peak prey abundance and marine productivity (Beamish et al 2008(Beamish et al , 2012, as well as due to domestication (Fritts et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Size, growth, and origin-dependent mortality of juvenile Chinook salmon Oncorhynchus tshawytscha during early ocean residence

Woodson¹,

Wells²,

Weber³

et al. 2013

Mar. Ecol. Prog. Ser.

103

135

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Selective mortality during early life history stages can have significant populationlevel consequences, yet critical periods when selective mortality occurs, the strength of selection, and under what environmental conditions can be difficult to identify. Here, we used otolith microstructure and chemistry to examine the factors potentially linked to selective mortality of juvenile fall-run Chinook salmon Oncorhynchus tshawytscha from California's Central Valley during early ocean residence. Back-calculated size and growth rates of the population were compared across 3 sample periods: as juveniles exited the San Francisco Bay estuary (estuary-exit), after their first month at sea (summer-ocean) and 5 mo after ocean entry (fall-ocean). We compared mortality dynamics during years of exceptional recruitment (addition of individuals to harvestable population; 2000 and 2001) to a year of poor recruitment (2005). Otoliths from 2005 were also analyzed for sulfur isotopes to discern hatchery from naturally spawned stock. Significant size and growth-rate selective mortality were detected during the first month at sea in the low recruitment year of 2005, but not in 2000 and 2001. Individuals that were larger and growing faster during freshwater and estuarine rearing were more likely to survive to summer and fall in the low recruitment year. There was a slight, but insignificant, increase in the proportion of hatchery to naturally spawned individuals from estuary-exit to fall-ocean, suggesting that fish from neither origin were overwhelmingly favored. Our results suggest that Central Valley Chinook salmon can be subject to significant size and growth-rate selective mortality resulting in low adult abundance, and this mortality appears independent of origin.

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Section: Introductionmentioning

confidence: 99%

Size, growth, and origin-dependent mortality of juvenile Chinook salmon Oncorhynchus tshawytscha during early ocean residence

Woodson¹,

Wells²,

Weber³

et al. 2013

Mar. Ecol. Prog. Ser.

103

135

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“…To the best of our knowledge, of the studies that have linked marine climate variability and salmon abundance to changes in sizeat-age (Martinson et al 2008;Ruggerone et al 2012;Agler et al 2013;McPhee et al 2016;Yasumiishi et al 2016) and survival (e.g., Levin et al 2001), none have used repeated measures of growth accounting for correlation among individuals within a single model (but see Marco-Rius et al 2013 on freshwater growth patterns of sea trout, Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

Marine growth patterns of southern British Columbia chum salmon explained by interactions between density-dependent competition and changing climate

Debertin

Irvine

Holt

et al. 2017

Can. J. Fish. Aquat. Sci.

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Thirty-nine years of scale growth measurements from Big Qualicum River chum salmon (Oncorhynchus keta) in southern British Columbia demonstrated that competition and climate variation affect marine growth and age-at-maturity. A longitudinal study design that accounted for correlation among individuals revealed growth at all ages was reduced when the biomass of North American chum, sockeye (Oncorhynchus nerka), and pink salmon (Oncorhynchus gorbuscha) was high. When North Pacific Gyre Oscillation (NPGO) was positive, indicating increased primary productivity, predicted growth increased. Climate variation influenced competition effects. For instance, density-dependent competition effects increased when NPGO became more positive and Pacific Decadal Oscillation became more negative (indicating cool conditions), causing the greatest range in predicted scale size. Chum salmon are likely to exhibit continued reduction in growth at age due to increased ocean temperatures driven by climate change and high aggregate salmon biomass that includes hatchery releases. If evidence of biomass and climate effects presented here are common among Pacific salmon populations, reduction of hatchery releases should be considered. Résumé :Des mesures sur 39 ans de la croissance des écailles de saumons kétas (Oncorhynchus keta) de la Grande rivière Qualicum, dans le sud de la Colombie-Britannique, démontrent que la concurrence et les variations climatiques ont une incidence sur la croissance en mer et l'âge à la maturité. Un plan d'étude longitudinale qui tient compte de la corrélation entre individus révèle que la croissance à tous les âges est plus faible quand la biomasse des saumons kétas, sockeyes (Oncorhynchus nerka) et roses (Oncorhynchus gorbuscha) d'Amérique du Nord est élevée. Quand l'oscillation du tourbillon nord-pacifique (OTPN) est positive, indiquant une productivité primaire accrue, la croissance prédite augmente. Les variations du climat ont également une incidence sur ces effets de concurrence. Les effets de la concurrence dépendant de la densité augmentent quand l'OTPN devient plus positive et l'oscillation décennale du Pacifique, plus négative (indiquant des conditions fraîches), ce qui produit la plus grande fourchette de tailles d'écailles prédites. Il est probable que les saumons kétas continueront de présenter une diminution de la croissance selon l'âge en raison de la hausse des températures océaniques causée par les changements climatiques et de la forte biomasse totale de saumons incluant les individus issus d'écloseries. Si les indices d'effets de la biomasse et du climat relevés dans la présente étude s'avéraient répandus dans les populations de saumons du Pacifique, il serait pertinent d'examiner la possibilité de réduire les lâchers de poissons issus d'écloseries. [Traduit par la Rédaction]

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“…Salmonid species are commonly used in hatchery programmes aimed to supplement or restore declining wild populations (Levin et al 2001). However, hatcheries generally keep fish at high densities in plain rearing tanks, where they receive plenty of nutritious pellets, so that there is no need for hatchery fish to actively search for food.…”

Section: Introductionmentioning

confidence: 99%

Less is more: density influences the development of behavioural life skills in trout

2010

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Theory suggests that habitat structure and population density profoundly influence the phenotypic development of animals. Here, we predicted that reduced rearing density and increased structural complexity promote food search ability, anti-predator response and the ability to forage on novel prey, all behavioural skills important for surviving in the wild. Brown trout were reared at three densities (conventional hatchery density, a fourth of conventional hatchery density and natural density) in tanks with or without structure. Treatment effects on behaviour were studied on trout fry and parr, whereupon 20 trout from each of the six treatment groups were released in an enclosed natural stream and recaptured after 36 days. Fry reared at natural density were faster to find prey in a maze. Moreover, parr reared at natural density were faster to eat novel prey, and showed more efficient anti-predator behaviour than fish reared at higher densities. Furthermore, parr reared at reduced densities were twice as likely to survive in the stream as trout reared at high density. In contrast, we found no clear treatment effects of structure. These novel results suggest that reduced rearing densities can facilitate the development of behavioural life skills in captive animals, thereby increasing their contribution to natural production.

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The road to extinction is paved with good intentions: negative association of fish hatcheries with threatened salmon

Cited by 166 publications

References 23 publications

Size, growth, and origin-dependent mortality of juvenile Chinook salmon Oncorhynchus tshawytscha during early ocean residence

Size, growth, and origin-dependent mortality of juvenile Chinook salmon Oncorhynchus tshawytscha during early ocean residence

Marine growth patterns of southern British Columbia chum salmon explained by interactions between density-dependent competition and changing climate

Less is more: density influences the development of behavioural life skills in trout

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