摘要
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We observed diel vertical migration patterns in juvenile pink salmon (<i>Oncorhynchus gorbuscha</i> (Walbaum, 1792)) and tested the hypothesis that fish behaviour is altered by exposure to sea lice copepodids. Experiments involved...
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We observed diel vertical migration patterns in juvenile pink salmon (<i>Oncorhynchus gorbuscha</i> (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 (<i>Lepeophtheirus salmonis</i> (Kroyer, 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 <i>L. salmonis</i> 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.
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