No abstract

The effects of climate events on the feeding ecology and trophic dynamics of Pacific salmon (Oncorhynchus spp.) in offshore waters of the central Gulf of Alaska were investigated during early summers (1994)(1995)(1996)(1997)(1998)(1999)(2000), based on analyses of stomach contents, and carbon and nitrogen stable isotopes (d 13 C and d 15 N). Gonatid squids (mainly Berryteuthis anonychus) were the dominant prey of all salmon species except for chum salmon (O. keta). During the 1997 El Niñ o event and the 1999 La Niñ a event, squids decreased sharply in the diets of all Pacific salmon except coho salmon (O. kisutch) in the Subarctic Current, and chum salmon diets changed from gelatinous zooplankton (1995-97) to a more diverse array of zooplankton species. A d 13 C and d 15 N analysis indicated that all salmon species occupied the same branch of the food web in 1999-2000. We hypothesize that high-seas salmon adapt to climate-induced changes in their prey resources by switching their diets either within or between trophic levels. To understand the effects of climate change on Pacific salmon in the Gulf of Alaska, biological oceanographic research on B. anonychus and other important prey resources is needed.

No abstract

The relationship between mean weights of hatchery-reared masu salmon Oncorhynchus masou smolts at release and the subsequent recovery rates by coastal commercial fisheries in Hokkaido, northern Japan, was investigated using the maximum likelihood method. A strongly positive correlation was observed, showing smolts with a mean of 32.6 g obtained an approximately 20-fold recovery rate of those with a mean of 14.8 g. The model with log-transformed independent variable (Y i = -11.237 + 4.239 ln X i ) was selected as the most parsimonious model to represent the release size (X i ) and recovery rate (Y i ) relationship. KEY WORDS: Akaike information criterion, masu salmon, maximum likelihood method,Oncorhynchus masou, smolt size.

In spite of a relatively optimistic pre-season forecast, the total return of adult sockeye salmon (Oncorhynchus nerka) to the Fraser River (British Columbia, Canada) in 2009 was the lowest recorded since quantitative records began in the late 1940s. A plausible mechanism is proposed that links a sequence of extreme oceanic and climatic events to poor marine survival. It began with record-setting snow packs in the coastal mountain range during the