| Summary: | Modern salmon aquaculture began in 1970 with the innovation of at-sea fish pens which precipitated a rapid growth in production. The expansion of the industry and increased number of farmed fish concentrated within the open net-pens has produced conditions that foster environmental and disease problems. Among the various pathogens impacting the industry, the salmon louse (Lepeophtheirus salmonis) presents a unique challenge due to its proliferation on farms, welfare impacts on host fish, the threat it poses to wild populations of salmonids, and for the cost of and its resistance to control efforts. Norway, the world leader in salmon production, has responded to the persistent challenge of salmon lice with the implementation of a management regime (Traffic Light System) that links permitted aquaculture production to louse induced mortality of wild Atlantic salmon populations. Those management decisions are reliant on an understanding of salmon louse distribution throughout the Norwegian coast, but aspects of the copepod’s life history and biology which determine their planktonic abundance remain understudied. Nevertheless, to meet the needs of the management regime modelers must forecast salmon louse reproduction and planktonic dispersal from salmon farms. Although these models are validated with observations of salmon louse infections on fish, there is a lack of empirical evidence on the distribution and abundance of planktonic stages. Due to the difficulty of enumerating planktonic lice in a mixed zooplankton sample they are almost unobservable and thus exist in a ‘black-box’. This thesis seeks to shed light on the salmon louse larval black-box within the context of the aquaculture management in Norway through two approaches. A greater knowledge of the planktonic stages can be gained through a better understanding of the salmon louse’s life history, and through empirical data on their planktonic abundance and distribution. This thesis addresses the first approach by refining the current understanding of salmon ...
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