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Effect of Lamprey Attachment on Profile Drag of Lake Trout: Consequences for Swimming
1 Jeff W. Dawson and 1Ryan J. Chlebak
1 Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa ON K1S 5B6.
Lake trout mortality due to sea lamprey parasitism can be as great as 60% due to blood loss and tissue and organ damage during feeding which can last from 2 to 10 days. During this period, trout must continue to swim to find food and avoid predators. The hydrodynamic cost of having an attached lamprey, therefore, represents an additional bioenergetic cost and may contribute to the high rate of mortality. The overarching objective of this pilot study was to determine the drag force (profile drag) acting on a parasitized trout. We accomplished this goal by using instrumented physical (3D printed) models of trout (lake trout, ‘lean’ variety) with and without model lamprey of different sizes attached at differing locations on the trout body. Model lamprey attached to the model, both in the pectoral fin region, and the pelvic fin region, increased profile drag. Larger lamprey increased drag more than smaller lamprey, as expected. But, similar sized lamprey models attached to the pectoral region produced more drag than when attached to the pelvic region which was unexpected. Trout with two lamprey attached produce more drag than trout with single lamprey attached but we have insufficient data to fully understand how multiple lamprey attachment affects profile drag; but we suggest an important determinant is attachment location of each lamprey. This project bridged both sea lamprey and fisheries research and used a unique approach for studying the physical ecology of fish-lamprey interaction. The data on the physical costs of lamprey attachment (drag forces and force coefficients) will be useful for future bioenergetics models used to predict trout survival. This study also demonstrated the utility of a biomechanical methodology employing physical models that is also useful for studying other Great Lake fish species subject to sea lamprey predation.