Search

Copyright of Canadian Journal of Fisheries & Aquatic Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Shallow (5-35 m depth) coastal waters, with their proximity to human populations, are likely to experience greater changes to ecosystem structure and functions from climate change and human impacts than offshore waters. Concerns of declining fisheries landings and deteriorating habitat quality in Northumberland Strait led to an assessment by Fisheries and Oceans Canada of the state of the environment and biota including zooplankton during the summer. In this paper we describe spatial structure of zooplankton (three distinct assemblages) and determined that two oceanographic zones can explain the spatial variation. Using distance-based linear models, bottom water temperature and surface water salinity explained 16% to 25% of the variation in zooplankton composition for each year of the survey. We used retrospective analyses to estimate what the zooplankton assemblage may have resembled in the early 1990s from data of oceanographic conditions. Given the prediction of warming oceans by the Intergovernmental Panel on Climate Change, we provide a means of predicting zooplankton composition and their distribution, with implications for the planktivorous fishes that prey upon them. [ABSTRACT FROM AUTHOR]

Thirty-nine years of scale growth measurements from Big Qualicum River chum salmon ( Oncorhynchus keta) in southern British Columbia demonstrated that competition and climate variation affect marine growth and age-at-maturity. A longitudinal study design that accounted for correlation among individuals revealed growth at all ages was reduced when the biomass of North American chum, sockeye ( Oncorhynchus nerka), and pink salmon ( Oncorhynchus gorbuscha) was high. When North Pacific Gyre Oscillation (NPGO) was positive, indicating increased primary productivity, predicted growth increased. Climate variation influenced competition effects. For instance, density-dependent competition effects increased when NPGO became more positive and Pacific Decadal Oscillation became more negative (indicating cool conditions), causing the greatest range in predicted scale size. Chum salmon are likely to exhibit continued reduction in growth at age due to increased ocean temperatures driven by climate change and high aggregate salmon biomass that includes hatchery releases. If evidence of biomass and climate effects presented here are common among Pacific salmon populations, reduction of hatchery releases should be considered. [ABSTRACT FROM AUTHOR]