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Marine Ecology Progress Series

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MEPS 481:249-268 (2013)  -  DOI:

Long-term variation in common dolphin diet in relation to prey abundance

M. Begoña Santos1,*, Imogen German1,2, Diana Correia1,3, Fiona L. Read1,2, Jose Martinez Cedeira4, Mara Caldas5, Alfredo López4, Francisco Velasco6, Graham J. Pierce

1Instituto Español de Oceanografía, Centro Oceanográfico de Vigo, PO Box 1552, 36200 Vigo, Spain
2Oceanlab, University of Aberdeen, Aberdeenshire AB41 6AA, UK
3University of Algarve, 8005-139 Faro, Portugal
4CEMMA, PO Box 15, 36380 Gondomar, Spain
5Investigación Planificación y Dessarrollo S.A., Paseo Imperial 10-12, Bajo, 28005 Madrid, Spain
6Instituto Español de Oceanografía, Centro Oceanográfico de Santander, Promontorio San Martín, s/n. PO Box 240, 39080 Santander, Spain

ABSTRACT: Understanding the effects of changes in prey abundance on predators is essential to predict responses of marine ecosystems to perturbation and ensure sustainable fishing. As abundant top predators feeding largely on commercially exploited fish, common dolphins Delphinus delphis are expected to be affected by fluctuations in fish abundance. Previous studies variously suggest that common dolphins show a preference for energy-rich species or that they are opportunistic predators. In the latter case, the intensity of predation on all prey species would be expected to vary in proportion to their abundances. If such relationships are seen for only a few prey species, and the importance of other species varies inversely with the abundance of these ‘preferred’ prey, this would indicate selective feeding. We suggest that studies on diet at the population level can provide insights into such individual-level foraging decisions. We analysed stomach contents from 514 stranded and by-caught common dolphins in Galicia (NW Spain), collected over 2 decades. The most important prey were sardine, blue whiting and hake. Using zero-inflated generalised additive models to deal with non-linear relationships and the high number of zeros in prey count data, we tested for evidence of ‘preference’ for the main prey species, as well as confirming the existence of ontogenetic, spatial and seasonal variation in diet. Relationships between diet and annual prey abundance do not conclusively confirm either opportunistic or selective predation, but there is more evidence for the former. Lack of evidence for selective predation on energy-rich sardine could be due to current low stock levels.

KEY WORDS: Diet selection · Sardine · Hake · Blue whiting · Feeding ecology · Zero-inflated models

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Cite this article as: Santos MB, German I, Correia D, Read FL and others (2013) Long-term variation in common dolphin diet in relation to prey abundance. Mar Ecol Prog Ser 481:249-268.

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