By-catch and drowning in harbour porpoises (<Emphasis Type="Italic">Phocoena phocoena</Emphasis>) stranded on the northern Dutch coast |
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Authors: | Nynke Osinga Pieter ‘t Hart Danny Morick |
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Institution: | (1) Seal Rehabilitation and Research Centre (SRRC), Hoofdstraat 94A, 9968 AG Pieterburen, The Netherlands |
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Abstract: | Stranding data and recorded post-mortem findings were studied for 153 harbour porpoises (Phocoena phocoena), which were collected by the Seal Rehabilitation and Research Centre (SRRC; Pieterburen, The Netherlands) in the period
1984–2006. Special consideration was given to ‘by-catch’ listed as a major cause of death. A distinct increase in the numbers
of strandings of porpoises along the Dutch coastline has occurred in the recent years of the studied period. This corresponds
to the number of porpoises observed in Dutch waters in the same period. Although strandings occurred throughout the entire
year, they were most frequent during the January to July period. By-catch and drowning were noted most frequent in the winter
and spring seasons (December–April). By-catch and drowned porpoises were found along the entire Dutch coastline. The numbers
of animals per area varied depending on the collection efforts. At post-mortem investigation, three probable causes of death
were identified most frequently: pneumonia, emaciation and by-catch/drowning. The by-catch and drowning rate was calculated
to vary between 7% and 19%. Overall, the percentages obtained from this study appeared to be in line with those established
by others in neighbouring countries. Varying fishing techniques are used in Dutch waters. A careful study of the fishing methods
involved and close co-operation with fishermen are required to determine effective measures to reduce the by-catch of porpoises. |
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Keywords: | Harbour porpoise Phocoena phocoena Stranding Fisheries By-catch Post-mortem findings The Netherlands |
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