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Discovery Passage Plankton Monitoring and Juvenile Salmon Assessment 2009

The effects of climate change on the world's largest ecosystem, the marine pelagic realm, are largely unknown (1). Although warming is occurring more slowly in the oceans than on land, the response of marine organisms to climate change appears to be faster than terrestrial counterparts (2). Furthermore, different species of marine organisms are responding to climate change at different rates, resulting in disruption among various levels in the marine food web (3). For example, the decline in abundance of key planktonic organisms, and changes in seasonality have been implicated in exacerbating the decline of fish stocks (3). Our research program strives to develop an ecological monitoring program to document the changes in seasonal variation occurring in the marine planktonic environment, and apply the information towards improving fisheries enhancement management practices.

In 2007 the BC Centre for Aquatic Health Sciences (a not-for-profit research facility) partnered with the Quinsam Hatchery and At'legay Fisheries Society to develop an environmental sampling program to assess the relationship between the timing of spring plankton blooms and the fitness of Coho salmon being reared for a local stock enhancement initiative. Plankton is an essential food source for young Coho salmon and a disconnect may be occurring between when the hatchery-raised fish are entering the sea versus the optimal period of food availability. To address this issue, plankton sampling is conducted twice weekly and temperature, salinity, zooplankton and phytoplankton in the nearshore environment are analyzed and recorded. The plankton monitoring component is complemented by surveys of the abundance and size of captured enhancement Coho salmon to estimate how much the fish have grown since being released in relation to available plankton conditions. Within two years it has not only become apparent that the release of fish to coincide with plankton blooms significantly increases their feeding success in the near shore environment; but the timing of plankton blooms can vary substantially between years. Our ultimate goal is to develop a streamlined set of criteria that could be used by hatcheries to help determine the optimal time to release juvenile salmon for increased survival.

References: (1) Richardson AJ & Schoeman DS. 2004. Science 305 1609-1612; (2) Richardson AJ & Poloczanska ES. 2008. Science 320: 1294-1295; 3. Edwards M & Richardson AJ. 2004. Nature 430: 881-884.

Authors: Elan Downey, Dr. Alexandra Eaves, Dr.Sonja Saksida

Institution: BC Centre for Aquatic Health Sciences, Campbell River, B.C

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