Densities of planktonicLepeophtheirus salmonisbefore and after an Atlantic salmon farm relocation

• Published in: Aquaculture Environment Interactions Vol. 1; no. 3; pp. 225 - 232
• Main Authors: Penston, Michael J., McBeath, Alastair J. A., Millar, Colin P.
• Format: Journal Article
• Language: English
• Published: Inter-Research 01-01-2011
• Subjects: Agricultural management; Farms; Fish culture; Larvae; Larval development; Lice; Nauplii; Plankton; Salmon; Seas
• ISSN: 1869-215X; 1869-7534

Relocating Atlantic salmonSalmo salarL. farms away from important salmonid rivers is possibly a means to reduceLepeophtheirus salmonis(Krøyer, 1837) interactions between farmed Atlantic salmon and wild salmonids. However, to date, no data have been presented on the consequences of salmon farm relocation in terms of densities of planktonicL. salmonis. Near-surface plankton were sampled at 5 stations during 2 full farming production cycles; 1 before and 1 after a salmon farm relocation within a sea loch/fjord. The relocation comprised the removal of a salmon farm and the reallocation of its fish biomass to a different farm within the same management area. Over 85% of the larval sea lice we identified in sub-samples wereL. salmonis; we therefore assumed that the majority of the larvae found were of that species. Densities ofL. salmonislarvae increased significantly at all stations post relocation, except at the station near the vacated farm site where mean densities of nauplii were significantly lower and mean densities of copepodids were lower without statistical significance. The removal/relocation of the salmon farm significantly reduced the production ofL. salmonislarvae, but did not significantly reduce the infection pressure, as represented by densities of the infectious copepodid stage, at the vacated farm site. This finding indicates that planktonicL. salmoniswere transported to the vacated farm site from sources at a minimum of 5 to 8 km distant.