Geology topics

A.D. Cross

Publications and source records attributed to A.D. Cross.

3 recordsLinked to original sources

USGS2011

Evidence for size-selective mortality after the first summer of ocean growth by pink salmon

Pink salmon Onchorhynchus gorbuscha with identifiable thermal otolith marks from Prince William Sound hatchery release groups during 2001 were used to test the hypothesis that faster-growing fish during their first summer in the ocean had higher survival rates than slower-growing fish. Marked juvenile pink salmon were sampled monthly in Prince William Sound and the Gulf of Alaska, and adults that survived to maturity were recovered at hatchery release sites the following year. Surviving fish exhibited significantly wider circuli spacing on the region of the scale formed during early marine residence than did juveniles collected at sea during their first ocean summer, indicating that marine survival after the first growing season was related to increases in early marine growth. At the same circuli, a significantly larger average scale radius for returning adults than for juveniles from the same hatchery would suggest that larger, faster-growing juveniles had a higher survival rate and that significant size-selective mortality occurred after the juveniles were sampled. Growth patterns inferred from intercirculi spacing on scales varied among hatchery release groups, suggesting that density-dependent processes differed among release groups and occurred across Prince William Sound and the coastal Gulf of Alaska. These observations support other studies that have found that larger, faster-growing fish are more likely to survive until maturity. ?? Copyright by the American Fisheries Society 2005.

Transactions of the American Fisheries Society↗

USGS2011

Early marine growth of pink salmon in Prince William Sound and the coastal gulf of Alaska during years of low and high survival

Although early marine growth has repeatedly been correlated with overall survival in Pacific salmon Oncorhynchus spp., we currently lack a mechanistic understanding of smolt-to-adult survival. Smolt-to-adult survival of pink salmon O. gorbuscha returning to Prince William Sound was lower than average for juveniles that entered marine waters in 2001 and 2003 (3% in both years), and high for those that entered the ocean in 2002 (9%) and 2004 (8%). We used circulus patterns from scales to determine how the early marine growth of juvenile pink salmon differed (1) seasonally during May-October, the period hypothesized to be critical for survival; (2) between years of low and high survival; and (3) between hatchery and wild fish. Juvenile pink salmon exhibited larger average size, migrated onto the continental shelf and out of the sampling area more quickly, and survived better during 2002 and 2004 than during 2001 and 2003. Pink salmon were consistently larger throughout the summer and early fall during 2002 and 2004 than during 2001 and 2003, indicating that larger, faster-growing juveniles experienced higher survival. Wild juvenile pink salmon were larger than hatchery fish during low-survival years, but no difference was observed during high-survival years. Differences in size among years were determined by some combination of growing conditions and early mortality, the strength of which could vary significantly among years. ?? Copyright by the American Fisheries Society 2008.

Transactions of the American Fisheries Society↗

USGS2009

Bioenergetic model estimates of interannual and spatial patterns in consumption demand and growth potential of juvenile pink salmon (Oncorhynchus gorbuscha) in the Gulf of Alaska

A bioenergetic model of juvenile pink salmon (Oncorhynchus gorbuscha) was used to estimate daily prey consumption and growth potential of four ocean habitats in the Gulf of Alaska during 2001 and 2002. Growth potential was not significantly higher in 2002 than in 2001 at an alpha level of 0.05 (P=0.073). Average differences in growth potential across habitats were minimal (slope habitat=0.844 g d -1 , shelf habitat=0.806 g d -1 , offshore habitat=0.820 g d -1 , and nearshore habitat=0.703 g d -1 ) and not significantly different (P=0.630). Consumption demand differed significantly between hatchery and wild stocks (P=0.035) when examined within year due to the interaction between hatchery verses wild origin and year. However, the overall effect of origin across years was not significant (P=0.705) due to similar total amounts of prey consumed by all juvenile pink salmon in both study years. We anticipated that years in which ocean survival was high would have had high growth potential, but this relationship did not prove to be true. Therefore, modeled growth potential may not be useful as a tool for forecasting survival of Prince William Sound hatchery pink salmon stocks. Significant differences in consumption demand and a two-fold difference in nearshore abundance during 2001 of hatchery and wild pink salmon confirmed the existence of strong and variable interannual competition and the importance of the nearshore region as being a potential competitive bottleneck.

Deep-Sea Research Part II: Topical Studies in Ocea↗