Spatiotemporal patterns of overlap between short-finned pilot whales and the U.S. pelagic longline fishery in the Mid-Atlantic Bight: an assessment to inform the management of fisheries bycatch

This research examined the spatial and temporal characteristics of pilot whale habitat use and longline fishing effort. The information was used to assess the potential for a spatial management approach to mitigate pilot whale bycatch. The Area Under the Curve and Williamson's Spatial Overlap Index were both used to assess patterns of overlap and bycatch by applying them to telemetry data from short-finned pilot whales, longline fishery effort and Pelagic Observer Program (POP) data (2014-2015). Based on this analysis, important variables influencing pilot whale-longline overlap and POP bycatch rates include: proximity to the 1000 m isobath, season, and sea surface temperature. Pilot whales had the highest density inshore of the 1000 m isobath. Longline effort along this isobath varies seasonally. Seasonal patterns in pilot whale-longline overlap relative to the 1000 m isobath were significantly correlated with POP bycatch rates, with the highest bycatch rates occurring in the fall and winter months. Based on these results, the authors suggest that a spatial management approach for this unsustainable bycatch warrants further investigation, and provide suggestions for changing how fisheries observers might be deployed to provide data helpful for evaluating a spatio-temporal management strategy for reducing pilot whale bycatch in eastern US pelagic longline fisheries.