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Marine Ecology Progress Series

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MEPS 388:273-291 (2009)  -  DOI:

Importance of biological parameters in assessing the status of Delphinus delphis

Sinéad Murphy1,2,*, Arliss Winship1, Willy Dabin3, Paul D. Jepson4, Rob Deaville4,  Robert J. Reid5, Chris Spurrier6, Emer Rogan2, Alfredo López7, Angel F. González8,  Fiona L. Read8, Marjan Addink9, Monica Silva10, Vincent Ridoux2, Jennifer A. Learmonth11, Graham J. Pierce11,12, Simon P. Northridge1

1Sea Mammal Research Unit, University of St Andrews, St Andrews KY16 8LB, UK
2Department of Zoology, Ecology and Plant Science, University College Cork, Cork, Ireland
3Centre de Recherche sur les Mammifères Marins, Institut du Littoral et de l’Environnement, Université de La Rochelle,
17071 La Rochelle, France
4Institute of Zoology, Regents Park, London NW1 4RY, UK
5Wildlife Unit, SAC Veterinary Services, Inverness IV2 4JZ, UK
6Natural History Museum, Cromwell Road, London SW7 5BD, UK
7CEMMA, Apdo. 15 – 36380 Gondomar, Pontevedra, Spain
8CSIC, Instituto de Investigaciones Marinas, Eduardo Cabello 6, 36208 Vigo, Spain
9National Museum of Natural History, Darwinweg 22300 RA, Leiden, The Netherlands
10Centro do Instituto do Mar (IMAR) da Universidade dos Açores, Dept de Oceanografia e Pescas, 9901-862 Horta, Portugal
11School of Biological Science, University of Aberdeen, Zoology Building, Tillydrone Avenue, Aberdeen AB242TZ, UK
12Instituto Español de Oceanografía, Centro Oceanográfico de Vigo, PO Box 1552, 36200 Vigo, Spain

ABSTRACT: Short-beaked common dolphins Delphinus delphis in the eastern North Atlantic (ENA) are subject to mortality due to entanglement in various types of fishing gear. However, for this region, there is no population-level information available on trends in abundance, (incidental) mortality rates or even the actual distributional range. Working under the assumption that only 1 population exists in ENA waters, the current study presents basic life history data and investigates whether biological information obtained from postmortem data is, in itself, useful for managing this population. Life history parameters were estimated by analysing postmortem data obtained over a 16 yr period by UK, Irish, French, Galician (northwest Spain) and Portuguese stranding and bycatch observer programmes. An annual pregnancy rate of 26%, a calving interval of 3.79 yr, an average age attained at sexual maturity of 8.22 yr and an average length at sexual maturity of 188 cm were determined. With respect to the findings based solely on mortality data, significance testing failed to detect differences that could be construed as evidence of the population exhibiting what might be density-dependent compensatory responses. The low annual pregnancy rate reported throughout the sampling period may suggest either that the level of anthropogenic mortality did not cause a substantial population level decline, or a prey base declining at approximately the same rate as the dolphin population. However, this approach alone does not facilitate an assessment of the current state of the D. delphis population in the ENA. Population abundance estimates, trends in abundance and knowledge of factors that affect the dynamics of the population, such as annual mortality rates in fisheries, temporal variations in prey abundance and effects of contaminants on reproductive activity, are required not only to set management objectives, but also to give context to cross-sectional life history information.

KEY WORDS: Common dolphin · Delphinus delphis · Life history · Density-dependent · Control group · Eastern North Atlantic

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Cite this article as: Murphy S, Winship A, Dabin W, Jepson PD and others (2009) Importance of biological parameters in assessing the status of Delphinus delphis. Mar Ecol Prog Ser 388:273-291.

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