An Incidence of Walleye Pollock Feeding on Salmon Young

Armstrong, Robert H.; Winslow, Peter C.

doi:10.1577/1548-8659(1968)97[202:aiowpf]2.0.co;2

Cited by 4 publications

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“…Although our model simulations indicated that adult pollock were the dominant predator in the system during the 2 years included in our simulations, it is likely that this was an anomalous condition and that herring, immature pollock, and various other gadids were the most important predators in other years. Several other studies have documented predation by herring and immature pollock on juvenile salmon without determining its importance to mortality during early sea life (Thorsteinson, 1962; Bakshtanskiy, 1964; Armstrong and Winslow, 1968).…”

Section: Discussionmentioning

confidence: 99%

“…The relatively highenergy content of these copepods (Platt et al , 1969) makes them an attractive food source for many fishes. Large calanoid copepods compose a major part of the diets of herring and pollock during this season (Dwyer et al , 1987;Coyle and Paul, 1992;Yoshida, 1994), but both species are also piscivorous (Armstrong and Winslow, 1968;Thorsteinson, 1962;Bakshtansky, 1965;Dwyer et al , 1987). We conjectured that feeding mode shifts toward piscivory among these larger individuals may modify the mortality rates of larval or juvenile lifestages predicted by bottom-up processes.…”

Section: Introductionmentioning

confidence: 97%

“…Large calanoid copepods compose a major part of the diets of herring and pollock during this season (Dwyer et al. , 1987; Coyle and Paul, 1992; Yoshida, 1994), but both species are also piscivorous (Armstrong and Winslow, 1968; Thorsteinson, 1962; Bakshtansky, 1965; Dwyer et al. , 1987).…”

Section: Introductionmentioning

confidence: 99%

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Ecological processes influencing mortality of juvenile pink salmon (Oncorhynchus gorbuscha) in Prince William Sound, Alaska

Willette

Cooney²,

Patrick

et al. 2001

Fisheries Oceanography

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Our collaborative work focused on understanding the system of mechanisms influencing the mortality of juvenile pink salmon (Oncorhynchus gorbuscha) in Prince William Sound, Alaska. Coordinated field studies, data analysis and numerical modelling projects were used to identify and explain the mechanisms and their roles in juvenile mortality. In particular, project studies addressed the identification of major fish and bird predators consuming juvenile salmon and the evaluation of three hypotheses linking these losses to (i) alternative prey for predators (prey‐switching hypothesis); (ii) salmon foraging behaviour (refuge‐dispersion hypothesis); and (iii) salmon size and growth (size‐refuge hypothesis). Two facultative planktivorous fishes, Pacific herring (Clupea pallasi) and walleye pollock (Theragra chalcogramma), probably consumed the most juvenile pink salmon each year, although other gadids were also important. Our prey‐switching hypothesis was supported by data indicating that herring and pollock switched to alternative nekton prey, including juvenile salmon, when the biomass of large copepods declined below about 0.2 g m−3. Model simulations were consistent with these findings, but simulations suggested that a June pteropod bloom also sheltered juvenile salmon from predation. Our refuge‐dispersion hypothesis was supported by data indicating a five‐fold increase in predation losses of juvenile salmon when salmon dispersed from nearshore habitats as the biomass of large copepods declined. Our size‐refuge hypothesis was supported by data indicating that size‐ and growth‐dependent vulnerabilities of salmon to predators were a function of predator and prey sizes and the timing of predation events. Our model simulations offered support for the efficacy of representing ecological processes affecting juvenile fishes as systems of coupled evolution equations representing both spatial distribution and physiological status. Simulations wherein model dimensionality was limited through construction of composite trophic groups reproduced the dominant patterns in salmon survival data. In our study, these composite trophic groups were six key zooplankton taxonomic groups, two categories of adult pelagic fishes, and from six to 12 groups for tagged hatchery‐reared juvenile salmon. Model simulations also suggested the importance of salmon density and predator size as important factors modifying the predation process.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Ecological processes influencing mortality of juvenile pink salmon (Oncorhynchus gorbuscha) in Prince William Sound, Alaska

Willette

Cooney²,

Patrick

et al. 2001

Fisheries Oceanography

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“…April 26, 1994). As adult anadromous fish approach the coast, and as the juveniles leave freshwater (or at high tides), their congregations are often subject to high levels of predation by several species of marine birds and mammals, including seals, sea lions, and small whales (Fiscus 1980;Juneau Empire, December 6, 1993), and some saltwater fishes (for example, walleye pollock [ Theragra chalcogrammus}--see Armstrong (1968)--and Pacific herring (Clupeus pallasi)).…”

Section: H Everest Personal Communication; Juneau Empir~mentioning

confidence: 99%

Anadromous Fish as Keystone Species in Vertebrate Communities

Willson¹,

Halupka

1995

Conservation Biology

282

191

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Abstra~ Many wildlife species feed on anadromous fishes of several life-history stage¢ There is evidence for some wildlife species that the availability of anadromous fish is critically important for survival or repro-~tor% In some regions anadromous fishes in fresh water appear to be keystone food resomrces for vertebrate arid scavenger~ forging an ecologically significant link between aquatic and terrestrial ecosysten~ The spatial distribution of attadromous fish in fresh water, including the occurren~ of runs in very small stream& has important consequences for wildlife biology (social interaction& distribution, activity patter~ possibly survivorsbip) and cottservation of biodiversity. Peces an~dromos como especies claves en his comunidades de vertebradosResumen: Muchas especies se alimentan de varios de los estadtos de desarrollo de peces anddromox Existe evidencia que indica que para algunas especies silvestres la disponibilidad de peces anddromos es de suma importancia para su supervivencia o su reproduccio~ En aigunas regione~ los peces anddromos en aguas dulces parecen set recursos alimenticios claves para los pmdadoms vertebrados y los carro~k, ro~ constitu. yendo un eslab6n ecol6gicamente significativo entre los sistemas acudricos y terrestre~ La distribuci6n espacial de los peces anddromos en aguas dulce~ incluyendo la presencia de "corridas" en arroyos muy peq~ ttene consecuencias importantes para la biologta de la vida stlvestre (interacciones sociale~ distribuci6rg patrones de actividaa~ postbiltdades de suprevivencia) y la conservaci6n de la biodiver$tdaaL

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The Role of Competition and Predation in the Decline of Pacific Salmon and Steelhead

Fresh¹

1997

Pacific Salmon &Amp; Their Ecosystems

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An Incidence of Walleye Pollock Feeding on Salmon Young

Cited by 4 publications

References 0 publications

Ecological processes influencing mortality of juvenile pink salmon (Oncorhynchus gorbuscha) in Prince William Sound, Alaska

Ecological processes influencing mortality of juvenile pink salmon (Oncorhynchus gorbuscha) in Prince William Sound, Alaska

Anadromous Fish as Keystone Species in Vertebrate Communities

The Role of Competition and Predation in the Decline of Pacific Salmon and Steelhead

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