Journal of the Marine Biological Association of the United Kingdom




FOOD & FEEDING

Variability in the diet of bottlenose dolphin, Tursiops truncatus, in Galician waters, north-western Spain, 1990–2005


M.B.  Santos a1a2c1, R.  Fernández a2a3, A.  López a3, J.A.  Martínez a3 and G.J.  Pierce a2
a1 Instituto Español de Oceanografía, Centro Oceanográfico de Vigo, PO Box 1552, 36200, Vigo, Spain
a2 School of Biological Sciences (Zoology), University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, Aberdeen, UK
a3 CEMMA, Apdo. 15, 36380 Gondomar, Pontevedra, Spain

Article author query
santos mb   [PubMed][Google Scholar] 
fernández r   [PubMed][Google Scholar] 
lópez a   [PubMed][Google Scholar] 
martínez ja   [PubMed][Google Scholar] 
pierce gj   [PubMed][Google Scholar] 

Abstract

We describe the diet of bottlenose dolphins Tursiops truncatus in Galician waters, north-western Spain, based on 82 non-empty stomachs recovered and analysed from stranded animals between 1990 and 2005, quantifying interannual and seasonal variation in the diet, as well as dietary variation related to sex and size. The most important prey species (in terms of numerical importance and biomass) were blue whiting (Micromesistius poutassou) and hake (Merluccius merluccius), both of high commercial importance in Galician waters. Most blue whiting eaten by dolphins were mature fish but the estimated total consumption was relatively low (around 10%) compared to Spanish fishery landings of this species. In contrast, most hake eaten by dolphins were probably immature but the estimated total consumption is more than 20% of current annual fishery landings. The diet of by-caught animals, which made up around one third of the sample, was very similar to that in the overall sample. Although bottlenose dolphins are often seen close inshore, evidence from the diet suggests that they feed at the shelf edge. Evidence was found of ontogenetic dietary shifts and differences between diets of male and female dolphins. There were also clear changes in average diet over the 16-year study period, although there was no evidence that they were in response to changes in fish abundance. The amount of hake in the diet remained stable against a background of falling local abundance while the amount of blue whiting declined despite an increase in spawning stock size.

(Published Online February 26 2007)
(Received July 12 2006)
(Accepted November 2 2006)


Correspondence:
c1 Corresponding author, e-mail: m.b.santos@vi.ieo.es