Reducing Bycatch of the Harbour Porpoise (Phocoena phocoena) in the Northwestern Atlantic

Defense Date


Document Type


Degree Name

M.S. Marine Biology

First Advisor

Keith Ronald


Incidental mortalities of marine mammals and other marine organisms have become a major problem in commercial fisheries in the last decade. Many populations of small odontocetes seem to be more vulnerable to incidental catch due to their size and wide distribution in the U.S. Northeastern waters. The harbour porpoise (Phocoena phocoena) is one of the most common victims of bycatch in the Northwestern Atlantic. The principal reason for this seems to be the feeding habit of the harbour porpoise which mainly preys on commercially valued fishes, such as capelin (Mallotus villosus), herring (Clupea harengus), mackerel (Scomber scombrus), and small gadoids. These incidental catches are causing a serious decline in porpoise populations.

Even though the problem is worldwide, very little has been done to mitigate bycatches, mainly because of the lack of knowledge of the porpoise's life cycle and exact distribution. Numbers of solutions have been proposed, however, to minimize incidental deaths of porpoises as well as the related financial loss from the fisheries. A combination of immediate measures and longer term solutions should control some of the problem. In order for these solutions to be effective, an accurate knowledge of the animal's distribution and life cycle is necessary.

The main objective of this review is to summarize the problems created in the fisheries, in order to determine which solution would be most effective so as to avoid the porpoises' incidental deaths and subsequent financial loss in the fish industry.

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