Large-scale Analysis of Atlantic Nova Scotia American Lobster (Homarus americanus) Landings with Respect to Habitat, Temperature, and Wind Conditions

Abstract

American lobster (Homarus americanus) landings per unit of habitat, calculated for 25 statistical districts (SD) of Atlantic Nova Scotia (N.S.), were consistently higher in northern Cape Breton (SD 1–7) and southwestern N.S. (SD 32–34) than from the eastern (SD 15–18) and southern (SD 22–31) shores. Analyses suggest that changes in lobster populations of Atlantic N.S. take place over distances in the order of 100 km and over periods of about 5 yr and that lobster abundance is not limited by habitat availability. Five large homogeneous regions subject to similar historical landing trends could be identified on the basis of their thermal characteristics. Regions of lowest lobster landings (SD 8–31) are oriented in the axis of dominant southwest winds, which generate coastal upwelling, resulting in the lowest cumulative number of degree-days and a high year-to-year variability. Conversely, the high landings recorded in southwestern N.S. can be related to warm and stable temperature conditions, allowing lobsters to enhance yearly thermal gains via winter migrations into deep (> 100 m), warm Slope water. The definition of homogeneous regions characterized by common historical landing trends and thermal regime suggests that lobster abundance in Atlantic N.S. is ultimately controlled by large-scale oceanographic processes.