Nigrán, Spain
Nigrán, Spain
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Fernandez R.,University of Aberdeen | Garcia-Tiscar S.,Autonomous University of Madrid | Santos M.B.,Spanish Institute of Oceanography | Lopez A.,CEMMA | And 4 more authors.
Marine Biology | Year: 2011

Skin and muscle from 43 bottlenose dolphins (38 juveniles/adults, 5 calves) stranded in NW Spain were analysed to determine whether stable isotope ratios (δ13C and δ15N) could be used to assess dietary variation, habitat segregation and population substructure. Results were compared with published stomach contents data. Stable isotope ratios from 17 known prey species were also determined. Isotope ratios of the main prey (blue whiting, hake) varied significantly in relation to fish body size. Dolphin calves showed significant heavy isotope enrichments compared to adult females. Excluding calves, δ15N decreased with increasing dolphin body size, probably related to an ontogenetic shift in diet towards species at lower trophic levels, e. g. on blue whiting as suggested by stomach content results. Bottlenose dolphins were divided into two putative populations (North, South) based on previous genetic studies, and values of δ13C and δ15N differed significantly between these two groups, confirming the existence of population structuring. © 2011 Springer-Verlag.

Fernandez R.,University of Aberdeen | Santos M.B.,Spanish Institute of Oceanography | Pierce G.J.,University of Aberdeen | Pierce G.J.,Spanish Institute of Oceanography | And 9 more authors.
Hydrobiologia | Year: 2011

In the NE Atlantic, evidence has been found of genetic discontinuities between Iberian bottlenose dolphins and those of Scotland and the Mediterranean. Here, we explored the genetic relationships between resident populations of dolphins from southern Galicia (NW Spain) and the Sado estuary (S Portugal), and their relationship with dolphins inhabiting neighbouring areas. A total of 91 skin and muscle samples were taken from stranded and biopsied animals between 1994 and 2008 in southern Galicia (N = 29), the Sado estuary (N = 5) and five other geographical locations (N = 57) including sites around the Iberian Peninsula, the Canary Islands and the Azores. Individuals were genotyped at 10 microsatellite loci and sequenced at the highly variable mitochondrial control region. From individual-based analyses of microsatellite data, dolphins from southern Galicia and the Sado estuary were assigned to an individual genetic population, though nine dolphins were identified as possible migrants between putative populations as their genetic makeup did not correspond with their geographical stranding location. Pairwise estimates of genetic differentiation (FST) based on mitochondrial and nuclear DNA also revealed genetic differences between populations. The existence of fine-scale population substructure should be considered in the future designation of Special Areas of Conservation (SACs) for the species, as required by the European Habitats Directive. © 2011 Springer Science+Business Media B.V.

Mendez-Fernandez P.,CNRS Coastal and Marine Environment Laboratory | Mendez-Fernandez P.,University of Minho | Bustamante P.,CNRS Coastal and Marine Environment Laboratory | Bode A.,Spanish Institute of Oceanography | And 9 more authors.
Journal of Experimental Marine Biology and Ecology | Year: 2012

The feeding ecology and habitat use of the most frequently sighted and/or regularly reported stranded or by-caught toothed whale species of the North Western Iberian Peninsula (NWIP) were examined, with a special focus on their trophic position (TP) and relationships with their prey. With this aim, the stable isotope ratios of carbon (δ 13C) and nitrogen (δ 15N) of common dolphin (Delphinus delphis), bottlenose dolphin (Tursiops truncatus), harbour porpoise (Phocoena phocoena), striped dolphin (Stenella coeruleolba) and long-finned pilot whale (Globicepahala melas) were analyzed in muscle samples taken from stranded and by-caught animals between 2004 and 2008. Stable isotopes were also measured in 17 species of fish and cephalopods previously identified as prey species, based on stomach content analyses, and in plankton. The trophic enrichment factors (TEF) were calculated for all five species and in addition, isotopic mixing models were applied to estimate the proportional contribution of each prey source to the diet of the common dolphin, which was the toothed whale species best sampled in our study. Plankton, fish and cephalopods exhibited an increasing trend in their δ 13C values (from -19.6% to -15.3%) along the offshore-inshore axis, with a less clear spatial pattern observed for δ 15N values. Striped dolphins exhibited the lowest mean δ 13C, δ 15N and TP values (-17.6%, 10.8% and 4.3, respectively), which confirms the oceanic character of this species and its lower trophic position when compared to the other toothed whales analyzed. The common dolphin exhibited mean δ 13C, δ 15N and TP values that were at an intermediate level (-17.0%, 11.7% and 4.7, respectively) and results of the mixing model indicated that blue whiting (Micromesistius poutassou) was the main component of the diet. The harbour porpoise, bottlenose dolphin and pilot whale exhibited higher and very similar isotopic compositions and TPs. The mean TEF obtained between predators and their main prey were 1.4% for δ 15N and 0.8% for δ 13C. These results provide information on stable isotope incorporation data for toothed whales, which are essential if conclusions are to be drawn in issues concerning trophic structures and habitat use in the NWIP. © 2012 Elsevier B.V.

Santos M.B.,Spanish Institute of Oceanography | German I.,Spanish Institute of Oceanography | German I.,University of Aberdeen | Correia D.,Spanish Institute of Oceanography | And 8 more authors.
Marine Ecology Progress Series | Year: 2013

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 zeroinflated 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. © Inter-Research 2013.

Pierce G.J.,Spanish Institute of Oceanography | Caldas M.,CEMMA | Cedeira J.,CEMMA | Santos M.B.,Spanish Institute of Oceanography | And 6 more authors.
Journal of the Marine Biological Association of the United Kingdom | Year: 2010

Since mid-2003, systematic monthly sightings surveys for cetaceans have been carried out in Galicia (north-west Spain) from observation points around the coastline, with the aim of providing baseline data on cetacean distribution and habitat use to underpin future conservation measures. Here we summarize results for September 2003 to October 2007. The most frequently recorded species were the bottlenose dolphin (Tursiops truncatus, seen during 10.7% of observation periods), common dolphin (Delphinus delphis, 3.7%), harbour porpoise (Phocoena phocoena, 1.6%), Risso's dolphin (Grampus griseus, 0.4%) and short-finned pilot whale (Globicephala melas, 0.2%). The three most common species showed different distribution patterns along the coast. In terms of habitat preferences, bottlenose dolphins were seen to be associated with more productive areas (areas with higher chlorophyll-a concentrations) where the continental shelf was wider while both common dolphins and harbour porpoises were seen most frequently in less productive areas where the continental shelf is narrowest. Possible reasons for differences in habitat use include differing diets. In Galician waters, all three main cetacean species feed primarily on fish that are common in shelf waters, and in the case of blue whiting (the most important species in the stomach contents of common and bottlenose dolphins) abundant also on the slope. All three cetaceans feed on blue whiting while scad is important in diets of common dolphin and porpoise. It is also possible that porpoises do not use areas frequented by bottlenose dolphins in order to avoid aggressive interactions. Retrospective evaluation of the sampling regime, using data from the 2500 observation periods during 2003-2007 suggests that the overall sightings rates for all species (taking into account observation time and between-site travel time) would be higher if average observation duration was increased to at least 40 minutes. On the other hand, confidence limits on sightings rates stabilized after around 1000 observation periods, suggesting that the number of sites visited or the frequency of visits could be substantially reduced.

Reboredo-Fernandez A.,University of Santiago de Compostela | Ares-Mazas E.,University of Santiago de Compostela | Martinez-Cedeira J.A.,CEMMA | Romero-Suances R.,University of Santiago de Compostela | And 3 more authors.
Parasitology Research | Year: 2014

The occurrence of Giardia and Cryptosporidium was investigated in cetacean specimens stranded on the northwestern coast of Spain (European Atlantic coast) by analysis of 65 samples of large intestine from eight species. The parasites were identified by direct immunofluorescence antibody test (IFAT) and by PCR amplification of the β-giardin gene, the ITS1-5.8S-ITS2 region and the SSU-rDNA gene of Giardia and the SSU-rDNA gene of Cryptosporidium. Giardia and Cryptosporidium were detected in 7 (10.8 %) and 9 samples (13.8 %), respectively. In two samples, co-infection with both parasites was observed. Giardia duodenalis assemblages A, C, D and F, and Cryptosporidium parvum were identified. This is the first report of G. duodenalis in Balaenoptera acutorostrata, Kogia breviceps and Stenella coeruleoalba and also the first report of Cryptosporidium sp. in B. acutorostrata and of C. parvum in S. coeruleoalba and Tursiops truncatus. These results extend the known host range of these waterborne enteroparasites. © 2014, Springer-Verlag Berlin Heidelberg.

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