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Changes in the occurrence of common dolphins, striped dolphins and harbour porpoises in the English Channel and Bay of Biscay

Published online by Cambridge University Press:  26 November 2008

Colin D. MacLeod*
Affiliation:
Biscay Dolphin Research Programme (BDRP), 108 Park Road, Farnborough, Hampshire, GU14 6LT, UK School of Biological Sciences (Zoology), University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK
Tom Brereton
Affiliation:
Biscay Dolphin Research Programme (BDRP), 108 Park Road, Farnborough, Hampshire, GU14 6LT, UK
Clive Martin
Affiliation:
Biscay Dolphin Research Programme (BDRP), 108 Park Road, Farnborough, Hampshire, GU14 6LT, UK
*
Correspondence should be addressed to: C.D. MacLeod, School of Biological Sciences (Zoology), University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK email: [email protected]

Abstract

Regular monitoring of the status of cetacean populations is essential for conservation, policy and management. By using a passenger ferry as a scientific research platform, this study provides information on seasonal, annual and longer-term changes in the occurrence of three cetacean species along a relatively fixed transect through the English Channel and the Bay of Biscay. Data were collected over an 11 year period through the Biscay Dolphin Research Programme (BDRP). Surveys were conducted every month from 1996–2006 between Portsmouth, England and Bilbao, Spain by a team of experienced observers using standard techniques. From a 0.125° by 0.125° grid, cells were surveyed in each year and where each species was recorded they were identified using a geographical information system (GIS). A rapid analytical method—species occupancy (defined as the proportion of surveyed cells that a species was detected in)—was used to assess whether there were any trends in occurrence over time for three cetacean species. From this analysis, a significant trend to increasing occurrence of harbour porpoises in summer months in the English Channel was identified. There were also increases in the occurrence of common dolphins in the English Channel in winter months and striped dolphins in the Bay of Biscay in winter months corresponding with a decrease in summer occurrence, across the study period. However, while consistent, these trends were not significant.

Type
Research Article
Copyright
Copyright © Marine Biological Association of the United Kingdom 2008

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