Date of Award

Spring 5-5-2023

Level of Access Assigned by Author

Open-Access Thesis

Language

English

Degree Name

Master of Science (MS)

Department

Animal Sciences

Advisor

Ian Bricknell

Second Committee Member

Damian Brady

Third Committee Member

Kelly Cole

Additional Committee Members

Mike Pietrak

Abstract

Atlantic salmon (Salmo salar L.) aquaculture production in Maine is a valuable contributor to the economy, the expansion of which has been challenged by the parasitic salmon louse Lepeophtheirus salmonis. As planktonic organisms, the life of the salmon louse is primarily dictated by the physical conditions of the environment: the temperature for development time, salinity for survival, and current velocity for transport. Salmon lice are obligate parasites for whom the successful infection of a suitable host is critical to completion of their life cycle. However, little is understood about the effects of current velocity on infection success. Hydrodynamic models are tools that describe the physical conditions of the marine environment and have been combined with particle tracking models to predict the dispersal of sea lice in salmon-farming areas in other countries, including Norway, Scotland, Canada, and the Faroe Islands. These models vary in scope, however, many lack a parameter for the effect of velocity on attachment. The purpose of the experiments conducted as part of this thesis is to provide such a parameter for inclusion in a model for sea lice dispersal in Cobscook Bay, one of the primary sites of net pen salmon farming in the United States.

PIT-tagged Atlantic salmon were challenged with a standardized dose of salmon lice at low, moderate, and high current velocities commonly experienced by salmon in net-pens in Cobscook Bay at 5, 10, and 15 cm sec-1 (0.10, 0.19, and 0.29 knots), respectively. Mean percent settlement was calculated for each velocity group, and a permutation-based ANOVA was conducted to determine if significant differences existed between groups. Percent settlement was significantly different in all three velocity groups, with optimum settlement occurring at moderate velocity, with high velocity resulting in the lowest average settlement success. The results of this study exhibit similar patterns to what has been observed in other studies and are discussed with respect to sentinel cage surveys previously conducted in Cobscook Bay.

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