Depredation by harbor seal and spiny dogfish in a Georges Bank gillnet fishery
2012
RAFFERTY, A. R. | BRAZER, E. O. JR | REINA, R. D.
Depredation can have economic, social and ecological impacts by decreasing fishery landings and threatening marine predator populations through increased risk of entanglement. This investigation quantified the loss of landings attributed to harbour seal, Phoca vitulina L., and spiny dogfish, Squalus acanthias L., depredation in the Georges Bank, Massachusetts, USA gillnet fishery. Approximately 1361âkg (2.38%) of fish was discarded from a total possible catch weight of nearly 57â300âkg because it was unsalable following depredation. Spiny dogfish accounted for 1134âkg (1.98%), and harbour seal accounted for 227âkg (0.40%) of discards. This represented an estimated US$2250 loss in profits from a total possible catch value of almost US$61â800, signifying a 3.64% marketâvalue loss during the assessment period. These results suggest that discarding due to harbour seal and spiny dogfish depredation results in a relatively small market loss to fishers, although additional information and research is needed before this can be confirmed. This study is the first on this subject in the fishery and provides baseline information on depredation rates that could be useful if harbour seal and spiny dogfish populations continue to increase.
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