Consequences of seasonal variation in reservoir water level for predatory fishes: linking visual foraging and prey densities

Canadian Journal of Fisheries and Aquatic Sciences
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Abstract

In reservoirs, seasonal drawdown can alter the physical environment and may influence predatory fish performance. We investigated the performance of lake trout (Salvelinus namaycush) in a western reservoir by coupling field measurements with visual foraging and bioenergetic models at four distinct states (early summer, mid-summer, late summer, and fall). The models suggested that lake trout prey, juvenile kokanee (Oncorhynchus nerka), are limited seasonally by suitable temperature and dissolved oxygen. Accordingly, prey densities were greatest in late summer when reservoir volume was lowest and fish were concentrated by stratification. Prey encounter rates (up to 68 fish·day−1) and predator consumption are also predicted to be greatest during late summer. However, our models suggested that turbidity negatively correlates with prey detection and consumption across reservoir states. Under the most turbid conditions, lake trout did not meet physiological demands; however, during less turbid periods, predator consumption reached maximum bioenergetic efficiency. Overall, our findings demonstrate that rapid reservoir fluctuations and associated abiotic conditions can influence predator–prey interactions, and our models describe the potential impacts of water level fluctuation on valuable sport fishes.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Consequences of seasonal variation in reservoir water level for predatory fishes: linking visual foraging and prey densities
Series title Canadian Journal of Fisheries and Aquatic Sciences
DOI 10.1139/cjfas-2015-0008
Volume 73
Issue 1
Year Published 2016
Language English
Publisher NRC Press
Contributing office(s) Coop Res Unit Seattle
Description 12 p.
First page 53
Last page 64
Online Only (Y/N) N
Additional Online Files (Y/N) N