Mortality of sea scallops Placopecten magellanicus in the Mid-Atlantic Bight: Comment on Stokesbury et al. (2011)

• Published in: Marine ecology. Progress series (Halstenbek) 2011-12, Vol.443, p.293-297
• Main Authors: Hart, DR, Shank, BV
• Format: Article
• Language: English
• Subjects: Marine; Placopecten magellanicus
• ISSN: 0171-8630; 1616-1599
• DOI: 10.3354/meps09517

Stokesbury et al. (2011; Mar Ecol Prog Ser 425:167-173) concluded that 10 billion sea scallops Placopecten magellanicus probably died from discarding during fishing operations between surveys in 2003 and 2004, based on the observed reduction in scallops between these 2 surveys. The reported mortality primarily occurred in a very large 2001 year class that was below commercial size in 2003-2004, whereas mortality rates were lower for larger commercial-sized scallops. This pattern is not consistent with mortality from discarding, because commercial scallop dredge gear is designed to retain commercial-sized scallops, allowing a substantial proportion of undersized scallops to escape through the dredge rings. Data from at-sea observers in the Mid-Atlantic indicate that only 319 million scallops were discarded during this period. Non-capture (incidental) fishing mortality was also too low to account for the observed mortality. However, juvenile scallop mortality due to predation increases with their density, primarily induced by crabs Cancer spp. The observed high mortality of juvenile scallops was therefore probably a result of increased predation, rather than discarding.