Seal Depredation in the Nantucket Sound (Northeast USA) Weir Fishery

Depredation is an operational interaction in which marine mammals remove or damage catch retained in fishing gear, causing financial losses to fisheries. Logbooks were used to document gray seal (Halichoerus grypus) depredation in the Nantucket Sound weir fishery (northeast USA) during the 2007-2012 fishing seasons. Estimated weight of fish and squid remnants attributable to seal depredation in weirs was recorded during daily fishing operations. Depredation occurred during 45% of weir hauls. Total weight of partially consumed catch was <1% of total catch weight, dominated by longfin inshore squid (Doryteuthis pealeii), Atlantic menhaden (Brevoortia tyrannus), sea robins (Prionotus spp.), and black sea bass (Centropristis striata). Summer flounder (Paralichthys dentatus) remnants accounted for the greatest proportion of partially consumed catch relative to total catch (5%), followed by C. striata (3%), D. pealeii (2%) and Prionotus spp. (2%). This method underestimates total catch loss due to the use of estimated weights of remnants and does not account for prey swallowed whole or seal disturbance of schooling species, which can reduce efficiency of passive fishing gears such as weirs. Seasonality of seal occurrence and prey availability should be considered in prey selectivity analyses to improve the understanding of seal diet.