| 1. |
- Malick, Michael J., et al.
(författare)
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Growth and survival in relation to body size of juvenile pink salmon in the northern Gulf of Alaska
- 2011
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Ingår i: Marine and Coastal Fisheries. - 1942-5120. ; 3:1, s. 261-270
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Tidskriftsartikel (refereegranskat)abstract
- The abundance of anadromous salmon is partially determined by size-selective mortality during the early marine life phase. Consequently, identifying the growth patterns of juvenile salmon during this life phase is important in understanding the dynamics of salmon populations. We examined patterns of early marine growth in juvenile pink salmon Oncorhynchus gorbuscha released by four hatcheries in Prince William Sound (PWS), Alaska, and explored how these patterns related to marine survival. Since larger individuals are thought to experience reduced mortality, we partitioned the data into weight-based quartiles and compared growth rates (% body weight/d) of all fish, the largest fish (top 25%), and the smallest fish (bottom 25%). Sampling occurred during summer 1997–2004 in PWS, the inshore Gulf of Alaska (GOA), and the offshore GOA. Growth rates varied significantly among years and sampling locations; however, the growth rate patterns were markedly similar among size-groups and hatcheries. Growth rates tended to be high in 1997, 2002, and 2004 and lower in 1998, 2001, and 2003. Fish sampled in the offshore GOA typically had faster growth rates than those sampled elsewhere, although this was less pronounced for the largest fish. For all size-groups, the relationship between survival and growth rate was strongest for fish captured in the offshore GOA and weakest for those captured in PWS, indicating that the likelihood of survival is greater for juveniles that migrate offshore earlier. The strength of the growth rate–survival relationship for pink salmon captured in the offshore GOA was similar among all size-groups, suggesting that once fish migrate offshore they are less vulnerable to size-selective predation.
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| 2. |
- Piccolo, John, et al.
(författare)
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Feeding intensity, diet, and survival in relation to body size of juvenile pink salmon
- 2009
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Konferensbidrag (refereegranskat)abstract
- Variations in body size and growth rates in a cohort of juvenile fish can lead to differences in the feeding ecology of different sized conspecifics, thus, increasing differential survival in the cohort. Consequently, identifying the relationships between body size, feeding ecology, and survival is important in understanding mortality of juvenile fishes during the early marine life phase. We used feeding intensity, diet composition, and growth rate data collected from juvenile pink salmon (Oncorhynchus gorbuscha) to investigate how feeding ecology differs between large and small conspecifics and how the growth rates of large and small individuals influences overall marine survivorship. The sampling occurred from 1997-2004 and encompassed three marine habitats in the northern Gulf of Alaska. Feeding intensity did not significantly differ between large and small individuals across all habitats. Diet composition varied more among years and habitats than between large and small individuals. Within a year and habitat the diet composition of large and small conspecifics differed more in offshore waters than the near shore habitats with larger pink salmon eating more fish and less large copepods than smaller conspecifics. Growth positively related to marine survival in all habitats. The growth of fish sampled in offshore habitats related stronger to survival than the growth of fish in the near shore habitats. Within the offshore waters, the growth rates of larger individuals better explained marine survival than the growth of smaller conspecifics. These results suggest that diet composition does differ between small and large conspecifics on small temporal and spatial scales, which may allow larger individuals to exploit bigger and more energy rich prey, resulting in increase survival of larger fish.
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| 3. |
- Armstrong, Janet L., et al.
(författare)
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Interannual and Spatial Feeding Patterns of Hatchery and Wild Juvenile Pink Salmon in the Gulf of Alaska in Years of Low and High Survival
- 2008
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Ingår i: Transactions of the American Fisheries Society 2008; 137: 1299-1316.
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Tidskriftsartikel (refereegranskat)abstract
- To improve understanding of the mechanisms affecting growth and survival, we evaluated the summer diets and feeding patterns (prey composition, energy density, and stomach fullness) of hatchery and wild juvenile pink salmon Oncorhynchus gorbuscha in Prince William Sound (PWS) and the northern coastal Gulf of Alaska (CGOA). Our study (19992004) included 2 years of low (3%), mid (5%), and high (89%) survival of PWS hatchery pink salmon. Because variations in diet should affect growth and ultimately survival, we expected that the variations in diet, growth, and survival would be correlated. During August in the CGOA, pteropod-dominated diets and higher gut fullness corresponded to high survival (59%), and copepod-dominated diets and lower gut fullness corresponded to low survival (3%). Within years, no significant differences were found in diet composition or gut fullness between hatchery and wild fish or among the four PWS hatchery stocks. Diets varied by water mass (habitat) as juveniles moved from PWS to more saline habitats in the CGOA. In July, when juveniles were most abundant in PWS, their diets were dominated by pteropods and hyperiid amphipods. The diets of fish that moved to inner-shelf (i.e., the least-saline) habitat in the CGOA in July were dominated by larvaceans in low-survival years and pteropods in high-survival years. Diet quality was higher in CGOA habitats than in PWS in July. In August, fish moved to the more productive, more saline water masses in the CGOA, where large copepods and pteropods were dominant prey and diet quality was better than in PWS. Our results indicate that spatial variation in the diets of juvenile pink salmon in July and the timing of migration to the CGOA play a critical role in marine growth and survival
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