Growth Rate Potential of Juvenile Sockeye Salmon in Warmer and Cooler Years on the Eastern Bering Sea Shelf

Edward V Farley,Marc Trudel

doi:10.1155/2009/640215

Abstract

A spatially explicit bioenergetics model was used to predict juvenile sockeye salmonOncorhynchus nerkagrowth rate potential (GRP) on the eastern Bering Sea shelf during years with cooler and warmer spring sea surface temperatures (SSTs). Annual averages of juvenile sockeye salmon GRP were generally lower among years with cooler SSTs and generally higher in offshore than nearshore regions of the eastern Bering Sea shelf during years with warmer SSTs. Juvenile sockeye salmon distribution was significantly (P<.05) related to GRP and their prey densities were positively related to spring SST (P<.05). Juvenile sockeye salmon GRP was more sensitive to changes in prey density and observed SSTs during years when spring SSTs were warmer (2002, 2003, and 2005). Our results suggest that the pelagic productivity on the eastern Bering Sea shelf was higher during years with warmer spring SSTs and highlight the importance of bottom-up control on the eastern Bering Sea ecosystem.

Highlights

Interannual differences in growth conditions in the ocean likely translate into annual variations in survival of juvenile, immature, and maturing Pacific salmon Oncorhynchus spp
Juvenile sockeye salmon were broadly distributed during warmer years and their distribution appears to reflect the fact that growth rate potential (GRP) was higher over a much broader area than during cooler years
Our findings suggest a possible connection between GRP of juvenile sockeye salmon during late summer—early fall and spring sea surface temperatures (SSTs) along the eastern Bering Sea shelf

Summary

Introduction

Interannual differences in growth conditions in the ocean likely translate into annual variations in survival of juvenile, immature, and maturing Pacific salmon Oncorhynchus spp. Ocean conditions are believed to play a pivotal role in constraining early marine growth of juvenile salmon. Sized-based natural mortality of juvenile coho salmon O. kisutch was hypothesized to be linked to available nutrients regulating the food supply and competition for food [4]. Previous work on juvenile sockeye salmon O. nerka along the eastern Bering Sea shelf suggested that smaller fish had lower survival [5] and that size, condition and offshore distribution of these fish were connected to bottom-up control of the trophic structure on the eastern Bering Sea shelf [6]. Linking salmon prey demand to prey supply and their dependence on habitat could provide insight into the complex dynamics between marine productivity and growth and survival of salmon

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Conclusion