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An analysis of dorsal edge markings in short-beaked common dolphins (Delphinus delphis) from the Bay of Gibraltar and the Moray Firth

Published online by Cambridge University Press:  11 August 2015

Connor Christian George Bamford
Affiliation:
Cetacean Research & Rescue Unit, PO Box 11307, Banff, Aberdeenshire AB45 3WB, UK
Kevin Peter Robinson*
Affiliation:
Cetacean Research & Rescue Unit, PO Box 11307, Banff, Aberdeenshire AB45 3WB, UK
*
Correspondence should be addressed to:K.P. Robinson, Cetacean Research & Rescue Unit, PO Box 11307, Banff, Aberdeenshire AB45 3WB, UK email: [email protected]

Abstract

In the present study, short-beaked common dolphins (Delphinus delphis L.) from the Bay of Gibraltar (GIB) and the Moray Firth (MF) were examined to document the relative frequency, distribution and shape of dorsal edge markings (DEMs) in the species and investigate potential causes for their occurrence. A dorsal fin layout system was used to map the relative positions and shapes of presenting DEMs along the anterior/posterior and upper/lower fin margin from 617 animals. A total of 1989 DEMs were extracted from the combined datasets, with individuals exhibiting between one and 11 nicks (median = 3). DEMs (in the form of tears, nicks, notches and indents) were primarily observed along the posterior trailing edges of fins, with the highest concentration being recorded in the upper region of the posterior fin (80.3%). Approximately 80% of all DEMs were round or rectangular in shape. Square (notched) and indented nick shapes were further recorded, but in significantly lower numbers. In contrast to all other nick shapes however, indented DEMs predominantly occurred along the anterior fin margin. Both natural and anthropogenic sources were implicated as causes of DEMs in the dataset. Interactions with fisheries were apparent in both GIB and MF animals and evidently present a threat to both populations. Indeed, the occurrence, prevalence and type of presenting DEM and/or fin injuries (e.g. missing fins or disfigurements) in the species may provide a useful measure of the type and intensity of fisheries interactions affecting different populations.

Type
Research Article
Copyright
Copyright © Marine Biological Association of the United Kingdom 2015 

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