A Comparison of the Feeding Ecology and Growth of Juvenile Pink Salmon (Oncorhynchus Gorbuscha) in Northcentral and Southwestern Prince William Sound, Alaska PDF Download
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Author: David Gerard Parker
Publisher:
ISBN:
Category : Fishes
Languages : en
Pages : 352
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Author: David Gerard Parker
Publisher:
ISBN:
Category : Fishes
Languages : en
Pages : 352
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Author: R.B. Spies
Publisher: Elsevier
ISBN: 0080469426
Category : Nature
Languages : en
Pages : 609
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This comprehensive text is a major synthesis on ecological change in the Gulf of Alaska. It encompasses the structural and annual changes, forces of change, long-ecological changes in the atmosphere and ocean, plankton, fish, birds and mammals, and the effects of the 1989 Exxon Valdez Oil Spill. With 5 major sections, Long-term Ecological Change in the Northern Gulf of Alaska first describes the physical features, the atmosphere and physical oceanography, the annual production cycle, the forage base for higher animals and trophic transfer, and the adaptations for survival in this changing environment for 9 portal species. Then, the major forces of change are introduced: climate, geophysics, fisheries and harvesting, species interactions, disease and contaminants. Next, the long-term records of change in physical factors and biological populations are presented, as well as the potential reasons for the biological changes. Following is the history of the Exxon Valdez oil spill and its long-term effects. And, finally, the emergent properties of the ecosystem are discussed and an attempt is made to weigh the importance of the major forcing factors in terms of their temporal and spatial scales of influence.* Examines important data on long-term change in the ecosystem and the forcing factors that are responsible for it * Provides an account of the 1989 Exxon Valdez oil spill with emphasis on the long-term effects * Describes the effects of climate change, geophysical change, species interactions, harvesting, disease, the 1989 oil spill, and marine contaminants on key populations of marine organisms
Author: Hans van Haren
Publisher:
ISBN:
Category : Dynamic meteorology
Languages : en
Pages : 644
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Author: Harold P. Batchelder
Publisher:
ISBN:
Category : Fishes
Languages : en
Pages : 396
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Author:
Publisher:
ISBN:
Category : Aquatic sciences
Languages : en
Pages : 694
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Author: David Lindsay Urquhart
Publisher:
ISBN:
Category : Fishes
Languages : en
Pages : 222
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Includes abstract.
Author: Erica Jenkins
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The ecological niche of a population is dynamic and will be affected by changes in the ecosystem and as a population migrates. An ontogenetic niche shift can also occur as organisms grow and can include changes in morphology, habitat, and feeding behaviour. Although they are the two most abundant salmon species, and are further augmented through hatchery stocking, it is unclear the degree to which the niches of juvenile pink salmon (Oncorhynchus gorbuscha) and chum salmon (O. keta) overlap. Furthermore, juvenile pink salmon and chum salmon undergo a period of rapid growth during their first summer at sea and it is unclear how their ecological niche changes with their ontogeny. Understanding the foodweb dynamics of juvenile salmon in the coastal marine environment is important because a large proportion of the overall mortality of salmon is thought to occur during their first summer at sea. The purpose of this study is to determine the degree to which the niches of juvenile pink salmon and chum salmon overlap, how their trophic position and food source changes as they grow into a new ontogenetic niche, and how these processes are affected by ocean conditions. I expected that years of poorer feeding conditions and increased competition would result in reduced trophic position and greater overlap of the niches of juvenile pink salmon and chum salmon. I hypothesized that juvenile salmon would shift their diet to a more offshore-based foodweb as they grew and that their trophic position would increase with size, but that the shift would be stronger when feeding conditions were improved. Statistical analysis showed evidence that the overlap of the niches of pink salmon and chum salmon increased when the abundance of salmon was high. Contrary to expectations, the trophic position of salmon appeared to decrease under favourable conditions. The trophic position of both pink salmon and chum salmon was higher in the southern portion of the study area, and increased when juvenile abundance was high. I suggest that the higher trophic position among juvenile salmon when there is more competition might result from increased reliance on gelatinous zooplankton, which are carnivorous, but a nutritionally poor food choice compared to other common prey items. The ontogenetic shift from summer to fall among juvenile salmon included a shift to a more offshore-based diet and a higher trophic position. In the northern portion of the study area, which was comprised of the southern reaches of the Alaska Coastal Current (ACC), the shift to an offshore-based food source was more pronounced than the trophic shift. In the southern portion of the study area, which included the Transition Domain (TD) between the ACC and the California Current System (CCS), the shift to a higher trophic position was more pronounced than the shift in food source. The results of this study suggest that if climate change leads to poorer feeding conditions, the niches of pink salmon and chum salmon may increasingly overlap when the abundance of these species is high. Hatchery stocking of these species may also contribute to this trend if it leads to a greater abundance of juvenile salmon in the coastal marine environment. There is evidence that the structure of the food web and the nature of the ontogenetic niche shift are very different in the ACC and the TD, and climate change and hatchery stocking will most likely affect these regions differently.
Author: Scott A. Bonar
Publisher: Washington, D.C. : U.S. Fish and Wildlife Service, National Wetlands Research Centre
ISBN:
Category : Coastal ecology
Languages : en
Pages : 32
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Author: Alison Danielle Cross
Publisher:
ISBN:
Category : Pink salmon
Languages : en
Pages : 412
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Author: Donald G. Mortensen
Publisher:
ISBN:
Category : Pink salmon
Languages : en
Pages : 12
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Book Description
