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UBC Theses and Dissertations

The growth and diet composition of sockeye salmon smolts in Rivers Inlet, British Columbia Ajmani, Asha Megan


In the early life history of sockeye salmon smolts, prey availability (quality and quantity) and growth are strongly linked. During this critical period, when ~ 90% of their mortality occurs, they must attain a critical size at which they have sufficient energy stores to survive their long migration with little predation impact, leading to better survival and higher returns. To determine patterns of growth of out-migrating sockeye salmon and to link inter-annual variations in growth to diet and seasonality of the zooplankton community, seine netting and zooplankton tows were conducted in May-June 2008, 2009, and 2010 in Rivers Inlet, British Columbia, a fjord with estuarine circulation. Growth rate, condition factor and mass-length relationships were calculated from length and mass data obtained from fresh fish. Stomachs were analyzed for total prey composition in terms of biomass and abundance. Growth rates were faster in 2009 and 2010 than in 2008; however, the condition factor was highest in 2010, and similar in 2009 and 2008. Mass-length relationships indicated that sockeye smolts were significantly heavier per unit length in 2010 (p < 0.05). Bottom-up controls on spring productivity acting through environmental forcing such as temperature and advection may be responsible for the slower growth in the 2008 out-migrating population of sockeye salmon smolts. In 2008, quality and quantity of prey available may have not provided enough energy to maintain metabolism and to support rapid growth, possibly due to a mismatch in timing between spring productivity and the migration of the smolts.

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