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Author: Natura Richardson
Publisher:
ISBN:
Category : Sockeye salmon
Languages : en
Pages : 180
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Much attention has been given to juvenile Sockeye Salmon (Oncorhynchus nerka) ecology with particular focus on pelagic food webs in deep nursery lakes. In contrast, this study took place at Afognak Lake, Alaska, to better understand juvenile Sockeye Salmon foraging ecology, potential consumer interactions, and metabolic opportunities and constraints in a shallow nursery lake. I collected fish every two weeks from Afognak Lake from May through August, 2013. I described ontogenetic and temporal variation in the diets of juvenile Sockeye Salmon and a potential competitor, adult Threespine Stickleback (Gasterosteus aculeatus). Notably, this study revealed that adult aquatic insects are an important prey item for lake rearing juveniles. Threespine Stickleback diets showed some overlap with diets of juvenile Sockeye Salmon; however, significant differences in diet composition suggest that Sockeye Salmon and Threespine Stickleback partition prey and habitat resources. I then used my field-derived temperature, demographic, and diet data as inputs to a bioenergetics model to estimate summer consumption rate and growth efficiency of juvenile Sockeye Salmon from Afognak Lake across a range of foraging scenarios. Consumption rate was greater and mean growth efficiency was lower for all littoral-use scenarios relative to pelagic-use scenarios. Further, daily consumption was lowest and mean growth efficiency was highest for model scenarios in which insects were a dominant component of the diet relative to scenarios in which zooplankton were the dominant prey. My findings highlight the importance of benthic-pelagic coupling in Sockeye Salmon nursery lakes and the potential for juveniles to navigate trade-offs between energy acquisition and thermal conditions across lake habitats.
Author: Natura Richardson
Publisher:
ISBN:
Category : Sockeye salmon
Languages : en
Pages : 180
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Book Description
Much attention has been given to juvenile Sockeye Salmon (Oncorhynchus nerka) ecology with particular focus on pelagic food webs in deep nursery lakes. In contrast, this study took place at Afognak Lake, Alaska, to better understand juvenile Sockeye Salmon foraging ecology, potential consumer interactions, and metabolic opportunities and constraints in a shallow nursery lake. I collected fish every two weeks from Afognak Lake from May through August, 2013. I described ontogenetic and temporal variation in the diets of juvenile Sockeye Salmon and a potential competitor, adult Threespine Stickleback (Gasterosteus aculeatus). Notably, this study revealed that adult aquatic insects are an important prey item for lake rearing juveniles. Threespine Stickleback diets showed some overlap with diets of juvenile Sockeye Salmon; however, significant differences in diet composition suggest that Sockeye Salmon and Threespine Stickleback partition prey and habitat resources. I then used my field-derived temperature, demographic, and diet data as inputs to a bioenergetics model to estimate summer consumption rate and growth efficiency of juvenile Sockeye Salmon from Afognak Lake across a range of foraging scenarios. Consumption rate was greater and mean growth efficiency was lower for all littoral-use scenarios relative to pelagic-use scenarios. Further, daily consumption was lowest and mean growth efficiency was highest for model scenarios in which insects were a dominant component of the diet relative to scenarios in which zooplankton were the dominant prey. My findings highlight the importance of benthic-pelagic coupling in Sockeye Salmon nursery lakes and the potential for juveniles to navigate trade-offs between energy acquisition and thermal conditions across lake habitats.
Author: Theodore R. Merrell
Publisher:
ISBN:
Category : Sockeye salmon
Languages : en
Pages : 80
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Author: Richard L. Wallace
Publisher:
ISBN:
Category : Estuarine ecology
Languages : en
Pages : 290
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A study of the distribution, relative abundance and diet of fishes sympatric with juvenile sockeye salmon, Oncorhynchus nerka (Walbaum), within the freshwater nursery areas of the Naknek River system was undertaken from 1961 to 1963. The study was part of an extensive investigation to determine what factors in the freshwater environment were limiting the size of the populations of sockeye salmon returning to the rivers of Bristol Bay, Alaska. The speties found associated with juvenile salmon in the limnetic zones of the Naknek system were the pond smelt, Hypomesus olidus (Pallas); the least cisco, Coregonus sardinella Valenciennes; the threespine stickleback, Gasterosteus aculeatus Linnaeus; and the ninespine stickleback, Pungitius pungitius (Linnaeus). Life history information was collected for these sympatric species. Tow nets were used to capture samples of fish from the limnetic portions of the nursery areas. Some samples were collected by beach seines, lake traps and otter trawls. Plankton samples were collected and compared to the diets of the limnetic fishes. Although some confusion has existed in the literature, I concluded that pond smelt of the Naknek system belong to Hypomesus olidus (Pallas). The populations of smelt were comprised of six age-groups in the late summer, but most specimens belonged to three age-groups. Most members of the species spawn in the spring of the fourth year of life. The estimated fecundity ranged from 900 to 4,300 eggs per female. Seven age-groups of least ciscoes were present in the populations of the Naknek system. The species in the Naknek system probably spawned for the first time in the fall of their fourth year. The estimated fecundity of two specimens was 4,006 and 14,380 eggs. Populations of three spine stickleback were comprised of three age-groups of fish. I was unable to assign ages to ninespine stickleback. Estimates of the fecundity of the species ranged from 116 to 456 eggs per female. All species studied were distributed throughout the Naknek system. The relative abundance of the fishes studied was variable between and within nursery areas and from year to year. The population densities of pond smelt and threespine stickleback were larger in the surface waters compared to the deep waters. The relative abundance of sockeye fry, yearlings and ninespine stickleback was greater in the surface stratum rather than the deep stratum in most nursery areas. The five main food items utilized by these limnetic species were cladocerans (Bosmina sp. and Daphnia sp.); copepods (cyclopoid copepods and Diaptomus sp.); and Dipteran insects. Analysis of the similarity of diets indicated that the diets of sockeye fry and pond smelt were more similar than were the diets of sockeye fry or yearlings and any other sympatric species. The diet of sockeye fry was more similar to that of either species of stickleback than was the diet of sockeye yearlings. An analysis of the food of various sizes of each species of fish indicated the diets of three age-groups of smelt were more similar than the diets of various age-groups of any other fish. The food composition of three age-groups of ciscoes and two size groups of both species of stickleback showed a strong positive correlation. The diets of sockeye fry and yearlings showed the weakest positive correlation of the species studied. All species of fish studied selectively fed on one or more components of the zooplankton. Daphnia sp. and cyclopoid copepods were strongly selected in Lake Coville. Cyclopoids were selected in South Bay. Bosmina sp. was selected from the waters of West End. In Lake Coville, the greatest potential competition for food probably existed between the large populations of pond smelt and sockeye fry. In the West End nursery area, potential competition between juvenile salmon and both species of stickleback may not be severe, depending on the age composition of the salmon population present in the nursery area. The possibility exists that the relatively low numbers of adult sockeye salmon returning to the comparatively rich lakes of the Naknek River system is due to the presence of large populations of sympatric species of fish. Each of these sympatric species feed on the same general types of food organisms as do the juvenile salmon and may affect the numbers of young salmon that leave the lake, and subsequently return from the ocean.
Author: David Gerard Parker
Publisher:
ISBN:
Category : Fishes
Languages : en
Pages : 352
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Author: Albert V. Tyler
Publisher:
ISBN:
Category : Sockeye salmon
Languages : en
Pages : 34
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Author: Edward Vincent Farley (Jr.)
Publisher:
ISBN:
Category : Sockeye salmon
Languages : en
Pages : 272
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"Predicting annual returns of Bristol Bay sockeye salmon (Oncorhynchus nerka) has been difficult due to large, unexplained variations in return strength. Ocean conditions, particularly during the first few months after salmon leave freshwater, are believed to have a strong influence on their early marine growth and survival. Limited historical and present research suggests that sea temperature can affect juvenile Bristol Bay distribution. During years with cool spring sea temperatures, juvenile sockeye salmon are distributed nearshore along the Alaska Peninsula, whereas they are found further offshore during years with warm spring sea temperatures. Juvenile sockeye salmon are larger, in better condition, and have higher marine stage survival after the first year at sea when they are distributed further offshore than when they are distributed nearshore along the Alaska Peninsula. Juvenile sockeye salmon stomach contents also shift from primarily Pacific sand lance (Ammodytes hexapterus) and euphausiids to age 0 walleye pollock (Theragra chalcogramma) when their distribution changes from nearshore to further offshore. Annual averages of juvenile sockeye salmon growth rate potential (GRP) were generally lower among years and regions with cool spring sea temperatures. In addition, juvenile sockeye salmon GRP was generally higher in offshore regions than nearshore regions of the eastern Bering Sea shelf. A sensitivity analysis indicated that juvenile sockeye salmon GRP was more sensitive to changes in observed (August to September) sea surface temperatures during years when prey densities were lower. The results of the dissertation suggest that variability in early marine survival is primarily due to bottom-up control of the trophic structure of the eastern Bering Sea ecosystem"--Leaf iii.
Author: Bruce Charles McIntosh
Publisher:
ISBN:
Category : Decapoda (Crustacea)
Languages : en
Pages : 190
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"The diet and feeding behavior of maturing sockeye salmon (Oncorhynchus nerka) were investigated during the final marine phase of the spawning migration, prior to reentering natal streams. The stomach contents of commercially caught sockeye salmon, migrating within the nearshore waters of the Kodiak Archipelago during 1998 and 1999, were examined to determine the level of feeding activity and taxa of dominant prey items. Samples were collected throughout the majority of the migration (early June to late August) from areas known to be used principally as migration corridors, and from areas proximate to several natal streams. Dominant prey of sockeye salmon were decapod larvae, Pacific sandlance (Ammodytes hexapterus), and the pteropod Limacina helicina. Feeding activity levels and dominant prey taxa varied both between areas and within areas over time. Feeding activity levels for the population appear to gradually diminish, rather than abruptly ceasing, as sockeye approach their natal streams to spawn"--Leaf iii.
Author: Robert J. Ellis
Publisher: Forgotten Books
ISBN: 9780666598868
Category : Business & Economics
Languages : en
Pages : 24
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Excerpt from Possible Management Procedures for Increasing Production of Sockeye Salmon Smolts in the Naknek River System, Bristol Bay, Alaska In freshwater, juvenile sockeye salmon typically occupy four successive habitats for varying periods: spawning gravels of streams or lake beaches for several months, littoral of lakes for a few weeks, Open water areas of the lakes for several months to 2 or 3 yr, and an outlet river through which the smolts travel for a few hours or days to reach the ocean. Two factors seem most likely to limit the production of smolts: the quan tity and quality of spawning grounds, which may limit the number of fry produced, and the productivity of the pelagic waters of the lakes where juvenile salmon do most of their feeding and growing. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
Author: Brenda Joyce Rogers
Publisher:
ISBN:
Category : Fertilizers
Languages : en
Pages : 224
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Author: Ronald Albert Iverson
Publisher:
ISBN:
Category : Sockeye salmon
Languages : en
Pages : 144
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The life history of juvenile sockeye salmon (Oncorhynchus nerka) resident in Chignik River, Alaska, represents a departure from the lacustrine, pelagic existence typical of juveniles of this species. For this reason, the distribution, relative abundance in different parts of the river, growth, and upstream and downstream movements of juvenile sockeye in the river were studied during the summers of 1963 and 1964. The objectives of the study were to gain information on the possible origins of juvenile sockeye resident in Chignik River, and on the role of Chignik River in production of sockeye salmon. Distribution and abundance were estimated by seining and underwater observation. Juvenile sockeye appeared to be restricted to quiet waters along the shore. Catches of sockeye fry tended to increase through the summer, whereas catches of yearlings decreased. Smolts were taken in significant numbers only in June and July. early summer, large numbers of yearling sockeye were concentrated in Chignik River just below the outlet of Chignik Lake. In sockeye fry and yearlings captured in the lower river were generally larger than those captured in the upper river. Juvenile sockeye in the upper river grew slower than those in most other parts of the watershed. Scale analysis of sockeye salmon spawning in Chignik River showed that these fish entered the ocean at a larger size than did fish reared in Chignik Lake or Chignik River. This suggests that at least part of the progeny of river spawners do not remain in the river, but descend as fry to the brackish estuary, where growth conditions are superior. Upstream movement of schools of yearling sockeye was observed in the upper portions of the river. Such a movement has been observed many times in Chignik River in past years and has at times involved large numbers of fish. Schools of yearling sockeye have been observed to enter Chignik Lake. Fish of the same size group were captured while moving downstream at the lake outlet at night, suggesting a circular movement involving displacement of fish into the river at night and a positive rheotactic response causing them to re-enter the lake during the day. Juvenile sockeye salmon resident in Chignik River may include both progeny of river spawners, and fish which have moved down from Chignik Lake; Chignik Lake is probably the more important source. Chignik River is judged to have a minor role in the production of sockeye salmon, relative to the other rearing areas in the watershed.
