Diel vertical distribution of early marine phase juvenile pink salmon ( Oncorhynchus gorbuscha ) and behaviour when exposed to salmon louse ( Lepeophtheirus salmonis )

• Published in: Canadian Journal of Zoology
• Main Authors: Tang, S., Lewis, A.G., Sackville, M., Nendick, L., DiBacco, C., Brauner, C.J., Farrell, A.P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2011
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Oncorhynchus gorbuscha; Pink salmon
• Online Access: http://dx.doi.org/10.1139/z11-049; http://www.nrcresearchpress.com/doi/full-xml/10.1139/z11-049; http://www.nrcresearchpress.com/doi/pdf/10.1139/z11-049

We observed diel vertical migration patterns in juvenile pink salmon ( Oncorhynchus gorbuscha (Walbaum, 1792)) and tested the hypothesis that fish behaviour is altered by exposure to sea lice copepodids. Experiments involved replicated field deployments of a large (9 m) plankton column, which provided a vertical distribution enclosure under natural light and salinity conditions. Diel vertical distributions of juvenile pink salmon were observed during the first 3 weeks of seawater acclimation in both the presence and the absence of the ectoparasitic salmon louse ( Lepeophtheirus salmonis (Krøyer, 1838)). Immediately upon entering seawater, juvenile pink salmon preferred the top 1 m of the water column, but they moved significantly deeper down the vertical water column as seawater acclimation time increased. A significant diel migration pattern was observed, which involved a preference for the surface at night-time, compared with daytime. When fish in the column were exposed to L. salmonis copepodids for 3 h, 43%–62% of fish became infected, fish expanded their vertical distribution range, and significant changes in vertical distribution patterns were observed.