The early marine period for juvenile salmon is a critical life history stage for growth and survival. The health of near-shore ecosystems where juvenile salmon spend their early marine life, and the capacity of these habitats to provide prey are thus important for overall salmon returns. While near-shore habitat is generally accepted as being of critical importance, few studies have examined how juvenile salmon use this habitat during their early marine life. Understanding the trophic dynamics in these ecosystems and the characteristics of these habitats that are important for food provision will help us gauge the value of near-shore areas to the early marine phase of juvenile salmon. The importance of this avenue of research is underscored by declined rates of early marine survival of salmon, and suggestions that the rapid development of the shoreline is contributing to this decreased survival.
My project investigates the role that near-shore habitat plays in promoting growth and survival of juvenile salmon by evaluating eelgrass as foraging grounds for juvenile salmon in the Comox Estuary, British Columbia. In 2015, we compared juvenile Chum salmon diets to prey availability in zooplankton tows and in epifaunal and infaunal eelgrass samples across a gradient of eelgrass shoot density. We complemented diet analysis with the use of stable isotope ratios of carbon (δ13C) and nitrogen (δ13N) to examine the relative contribution of zooplankton, eelgrass, and terrestrial invertebrates to juvenile Chum salmon diet. In 2016, we collected additional eelgrass samples to cover a wider range of eelgrass density, and compared juvenile Chinook salmon diets to prey availability in eelgrass.
Prey invertebrates, such as polychaete worms, harpacticoid copepods, and amphipods, increased with eelgrass shoot density. Juvenile Chum salmon and juvenile Chinook salmon assessed in this study fed primarily on benthic species, specifically on harpacticoid copepods, which were only abundant in epifaunal eelgrass samples. The abundance of prey invertebrates in eelgrass beds and the benthic diet of juvenile salmon in the Comox Estuary leads us to conclude that the presence of eelgrass is an important habitat feature for juvenile salmon. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/7683 |
| Date | 21 December 2016 |
| Creators | Kennedy, Laura |
| Contributors | El-Sabaawi, Rana, Juanes, Francis |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | Available to the World Wide Web |
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