Movement of american lobster Homarus americanus associated with offshore mussel Mytilus edulis aquaculture

Abstract

Bivalve aquaculture sites attract a variety of large benthic species. Previous studies have shown that American lobsterHomarus americanusare more abundant in musselMytilus edulisfarms than in areas outside of them, suggesting that farms provide lobsters with adequate food and shelter. This study used acoustic telemetry to evaluate the influence of longline mussel farms on lobster movement behavior. In 2014, 60 lobsters were acoustically tagged on a boat and released in a mussel farm and at 2 reference sites outside the farm. Most lobsters (92%) left the monitored area within 1 d post-tagging; those released in reference sites moved northeast, whereas those released in the farm moved in random directions. Of the 16 lobsters that stayed or returned to the study area over the course of the 2 mo experiment, 10 displayed nomadic movements, 3 displayed small, local movements—presumably associated with foraging behavior, and 3 displayed both movements. The time lobsters spent within a site, distance travelled, and walking speed did not differ between the farm and reference sites. A second experiment was done in 2017 over 2 mo to evaluate tagging method (‘on boat’ andin situtagging) effects on lobster movement behavior. The experiment followed movements by 50 lobsters, half for each treatment, and showed that tagging method can affect walking speed during the first 24 h, but had no impact on the residence time and the distance travelled by the lobsters.