Search

Search Results

• 1. [Article] Ontogenetic shifts in diets of juvenile and subadult coho and chinook salmon in coastal marine waters: important for marine survival?

  Successfully shifting to a more piscivorous diet may be an important factor in the growth and survival of juvenile coho salmon Oncorhynchus kisutch and Chinook salmon O. tshawytscha during their first ...

  Citation × Citation Citation Abstract Copy Title: Ontogenetic shifts in diets of juvenile and subadult coho and chinook salmon in coastal marine waters: important for marine survival? Author: Weitkamp, Laurie A., Brodeur, Richard D., Daly, Elizabeth A. Successfully shifting to a more piscivorous diet may be an important factor in the growth and survival of juvenile coho salmon Oncorhynchus kisutch and Chinook salmon O. tshawytscha during their first summer in the northern California Current. Nonmetric multidimensional scaling and cluster analysis of diets by size showed several distinct groupings as the salmon grew during their first marine summer. These size-based diet differences were clearly driven by increased rates of piscivory for both species. Fish prey composition, feeding intensity, and fish prey-predator length ratios all significantly increased for coho salmon at approximately 240 mm fork length when they changed from diets dominated by juvenile rockfishes Sebastes spp., the larvae of crabs Cancer spp., and adult euphausiids to one of predominantly juvenile forage fish. As Chinook salmon grew, they gradually increased the proportional contribution (by weight) of fish prey in their diets-from 55% in the smallest length-class examined (80-100 mm) to 95% in the largest one (. 375 mm). Chinook salmon fed in the same marine environments as coho salmon and consistently ate more and longer fish prey at a given size than coho salmon but had lower overall feeding intensity, perhaps owing to a higher level of prey selection. Relating subsequent interannual adult salmon returns to juvenile diets showed mixed results. During lower-survival years, coho salmon ate fewer and smaller fish prey, while subyearling Chinook salmon had less total food and more empty stomachs. We did not find consistent trophic patterns for yearling Chinook salmon in relation to their ultimate survival. Title: Ontogenetic shifts in diets of juvenile and subadult coho and chinook salmon in coastal marine waters: important for marine survival? Author: Weitkamp, Laurie A., Brodeur, Richard D., Daly, Elizabeth A. Successfully shifting to a more piscivorous diet may be an important factor in the growth and survival of juvenile coho salmon Oncorhynchus kisutch and Chinook salmon O. tshawytscha during their first summer in the northern California Current. Nonmetric multidimensional scaling and cluster analysis of diets by size showed several distinct groupings as the salmon grew during their first marine summer. These size-based diet differences were clearly driven by increased rates of piscivory for both species. Fish prey composition, feeding intensity, and fish prey-predator length ratios all significantly increased for coho salmon at approximately 240 mm fork length when they changed from diets dominated by juvenile rockfishes Sebastes spp., the larvae of crabs Cancer spp., and adult euphausiids to one of predominantly juvenile forage fish. As Chinook salmon grew, they gradually increased the proportional contribution (by weight) of fish prey in their diets-from 55% in the smallest length-class examined (80-100 mm) to 95% in the largest one (. 375 mm). Chinook salmon fed in the same marine environments as coho salmon and consistently ate more and longer fish prey at a given size than coho salmon but had lower overall feeding intensity, perhaps owing to a higher level of prey selection. Relating subsequent interannual adult salmon returns to juvenile diets showed mixed results. During lower-survival years, coho salmon ate fewer and smaller fish prey, while subyearling Chinook salmon had less total food and more empty stomachs. We did not find consistent trophic patterns for yearling Chinook salmon in relation to their ultimate survival. Close

• 2. [Article] Marine distributions of chinook salmon from the West Coast of North America determined by coded wire tag recoveries

  The coded wire tag (CWT) database contains detailed information on millions of Pacific salmon Oncorhynchus spp. released from hatcheries or smolt traps and recovered in the north Pacific Ocean and its ...

  Citation × Citation Citation Abstract Copy Title: Marine distributions of chinook salmon from the West Coast of North America determined by coded wire tag recoveries Author: Weitkamp, Laurie A. The coded wire tag (CWT) database contains detailed information on millions of Pacific salmon Oncorhynchus spp. released from hatcheries or smolt traps and recovered in the north Pacific Ocean and its tributaries. I used this data set to examine the spatial and temporal variation in the marine distributions of 77 hatchery and 16 wild populations of Chinook salmon O. tshawytscha based on recoveries of an estimated 632,000 tagged salmon in coastal waters from southern California to the Bering Sea during 1979–1994 (and 1995–2004 for select hatcheries). Chinook salmon showed 12 distinct region-specific recovery patterns. Chinook salmon originating in a common freshwater region had similar marine distributions, which were distinct from those of adjacent regions. Different run types (e.g., spring, summer, and fall runs) originating in the same region exhibited variation in their marine distributions consistent with recovery at different stages of their ocean residence period. Recovery patterns were surprisingly stable across years, despite high interannual variation in ocean conditions. By contrast, ocean age influenced recovery patterns, as older fish were recovered further from their natal stream than younger fish. Although most of the CWT data used in the analysis came from hatchery fish, recoveries of tagged wild populations indicate patterns similar to those of fish from nearby hatcheries. The consistency in these findings across broad geographic areas suggests that they apply to Chinook salmon across the entire Pacific Rim. Similar findings for tagged coho salmon O. kisutch indicate that the observed patterns may apply to Pacific salmon as a whole and provide a model for other highly migratory fishes that have not benefited from such intensive tagging programs. The results also have implications for the genetic control of migration and salmon’s ability to respond to climate change. Title: Marine distributions of chinook salmon from the West Coast of North America determined by coded wire tag recoveries Author: Weitkamp, Laurie A. The coded wire tag (CWT) database contains detailed information on millions of Pacific salmon Oncorhynchus spp. released from hatcheries or smolt traps and recovered in the north Pacific Ocean and its tributaries. I used this data set to examine the spatial and temporal variation in the marine distributions of 77 hatchery and 16 wild populations of Chinook salmon O. tshawytscha based on recoveries of an estimated 632,000 tagged salmon in coastal waters from southern California to the Bering Sea during 1979–1994 (and 1995–2004 for select hatcheries). Chinook salmon showed 12 distinct region-specific recovery patterns. Chinook salmon originating in a common freshwater region had similar marine distributions, which were distinct from those of adjacent regions. Different run types (e.g., spring, summer, and fall runs) originating in the same region exhibited variation in their marine distributions consistent with recovery at different stages of their ocean residence period. Recovery patterns were surprisingly stable across years, despite high interannual variation in ocean conditions. By contrast, ocean age influenced recovery patterns, as older fish were recovered further from their natal stream than younger fish. Although most of the CWT data used in the analysis came from hatchery fish, recoveries of tagged wild populations indicate patterns similar to those of fish from nearby hatcheries. The consistency in these findings across broad geographic areas suggests that they apply to Chinook salmon across the entire Pacific Rim. Similar findings for tagged coho salmon O. kisutch indicate that the observed patterns may apply to Pacific salmon as a whole and provide a model for other highly migratory fishes that have not benefited from such intensive tagging programs. The results also have implications for the genetic control of migration and salmon’s ability to respond to climate change. Close

• 3. [Article] Spatial and trophic overlap of marked and unmarked Columbia River Basin spring Chinook salmon during early marine residence with implications for competition between hatchery and naturally produced fish

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Springer ...

  Citation × Citation Citation Abstract Copy Title: Spatial and trophic overlap of marked and unmarked Columbia River Basin spring Chinook salmon during early marine residence with implications for competition between hatchery and naturally produced fish Author: Teel, David J., Fisher, Joseph P., Beckman, Brian R., Weitkamp, Laurie A., Brodeur, Richard D., Daly, Elizabeth A. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Springer and can be found at: http://www.springer.com/?SGWID=0-102-0-0-0. Title: Spatial and trophic overlap of marked and unmarked Columbia River Basin spring Chinook salmon during early marine residence with implications for competition between hatchery and naturally produced fish Author: Teel, David J., Fisher, Joseph P., Beckman, Brian R., Weitkamp, Laurie A., Brodeur, Richard D., Daly, Elizabeth A. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Springer and can be found at: http://www.springer.com/?SGWID=0-102-0-0-0. Close

• 4. [Article] Buoyancy regulation by hatchery and wild coho salmon during the transition from freshwater to marine environments

  One aspect of diadromy that has received little attention is buoyancy regulation in fish moving between freshwater and marine environments. Because of density differences between the two water types, fish ...

  Citation × Citation Citation Abstract Copy Title: Buoyancy regulation by hatchery and wild coho salmon during the transition from freshwater to marine environments Author: Weitkamp, Laurie A. One aspect of diadromy that has received little attention is buoyancy regulation in fish moving between freshwater and marine environments. Because of density differences between the two water types, fish must alter their whole-fish density (WFD) or they will become positively (float) or negatively (sink) buoyant as they change environments. This idea was first suggested over 80 year ago but has been largely overlooked by the scientific community. To explore how fish regulate buoyancy during this important transition, I measured WFD and lipid levels and estimated swim bladder volumes (SBVs) of juvenile coho salmon Oncorhynchus kisutch collected from freshwater and marine environments. These fish exhibited increased WFD with increasingly dense environments, suggesting active buoyancy regulation. Most of the WFD increase was attributable to decreases in SBV, although hatchery coho salmon also exhibited decreased lipid levels with increasing WFD. Hatchery coho salmon had significantly higher lipid levels than wild coho salmon in both freshwater and marine environments. These high lipid levels may impede the ability of hatchery fish to regulate buoyancy and may increase their vulnerability to surface predators. Furthermore, lipid levels that vary with both environmental water density and fish origin clearly complicate the interpretation of this variable during the important transition from freshwater to the ocean. Title: Buoyancy regulation by hatchery and wild coho salmon during the transition from freshwater to marine environments Author: Weitkamp, Laurie A. One aspect of diadromy that has received little attention is buoyancy regulation in fish moving between freshwater and marine environments. Because of density differences between the two water types, fish must alter their whole-fish density (WFD) or they will become positively (float) or negatively (sink) buoyant as they change environments. This idea was first suggested over 80 year ago but has been largely overlooked by the scientific community. To explore how fish regulate buoyancy during this important transition, I measured WFD and lipid levels and estimated swim bladder volumes (SBVs) of juvenile coho salmon Oncorhynchus kisutch collected from freshwater and marine environments. These fish exhibited increased WFD with increasingly dense environments, suggesting active buoyancy regulation. Most of the WFD increase was attributable to decreases in SBV, although hatchery coho salmon also exhibited decreased lipid levels with increasing WFD. Hatchery coho salmon had significantly higher lipid levels than wild coho salmon in both freshwater and marine environments. These high lipid levels may impede the ability of hatchery fish to regulate buoyancy and may increase their vulnerability to surface predators. Furthermore, lipid levels that vary with both environmental water density and fish origin clearly complicate the interpretation of this variable during the important transition from freshwater to the ocean. Close

• 5. [Article] Seasonal and interannual variation in juvenile salmonids and associated fish assemblage in open waters of the lower Columbia River estuary

  This is the publisher’s final pdf. The published article is copyrighted by National Marine Fisheries Service, NOAA, Scientific Publications Office and can be found at: http://fishbull.noaa.gov/. To the ...

  Citation × Citation Citation Abstract Copy Title: Seasonal and interannual variation in juvenile salmonids and associated fish assemblage in open waters of the lower Columbia River estuary Author: Litz, Marisa N. C., Weitkamp, Laurie A., Bentley, Paul J. This is the publisher’s final pdf. The published article is copyrighted by National Marine Fisheries Service, NOAA, Scientific Publications Office and can be found at: http://fishbull.noaa.gov/. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. Title: Seasonal and interannual variation in juvenile salmonids and associated fish assemblage in open waters of the lower Columbia River estuary Author: Litz, Marisa N. C., Weitkamp, Laurie A., Bentley, Paul J. This is the publisher’s final pdf. The published article is copyrighted by National Marine Fisheries Service, NOAA, Scientific Publications Office and can be found at: http://fishbull.noaa.gov/. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. Close

• 6. [Article] Evidence for selective mortality in marine environments: the role of fish migration size, timing, and production type

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Inter-Research ...

  Citation × Citation Citation Abstract Copy Title: Evidence for selective mortality in marine environments: the role of fish migration size, timing, and production type Author: Teel, David J., Emmett, Robert L., Miller, Jessica A., Weitkamp, Laurie A., Claiborne, Andrew M. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Inter-Research and can be found at: http://www.int-res.com/journals/meps/meps-home/. Title: Evidence for selective mortality in marine environments: the role of fish migration size, timing, and production type Author: Teel, David J., Emmett, Robert L., Miller, Jessica A., Weitkamp, Laurie A., Claiborne, Andrew M. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Inter-Research and can be found at: http://www.int-res.com/journals/meps/meps-home/. Close