SALSEA North America: a pelagic ecosystem survey targeting Atlantic salmon in the Northwest Atlantic

Pelagic ecosystem surveys were conducted in the Labrador Sea during 2008 and 2009 as part of SALSEA North America. In total, 107 Atlantic salmon (Salmo salar) were captured using a pelagic surface trawl and multipanel surface gillnets. Surface trawling provided a broad spatial sampling of the fish and macroinvertebrate communities in the upper 10 m of the water column, but caught few salmon (23). Gillnetting was more effective at capturing post-smolt (60) and adult (24) salmon. Multiple smolt cohorts were captured, indicating that post-smolts and returning adults from different rivers in North America have similar autumnal habitat requirements. Post-smolts were caught at night and in water temperatures exceeding 10 degrees C, both novel results. Post-smolts and adults consumed similar and diverse prey species, although Themisto compressa was the most important prey item. Intestinal macroparasite loads were substantial and could be a significant source of mortality. Concurrent planktonic assemblage and oceanographic conditions were also quantified. A full exploration of these data, historical datasets, and parallel data collected during SALSEA Greenland and SALSEA-Merge will further understanding of the ecology of marine-phase Atlantic salmon and inform investigations into stock-specific differences in marine productivity.