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Fin whales (Balaenoptera physalus) aggregate west of Iceland during summer, where they feed mostly on krill, but their winter distribution is poorly known. This study investigates the winter behavior of fin whales that summer off Iceland by analyzing amino acid‐specific nitrogen isotope ratios in the baleen plates. This technique is increasingly used in large marine vertebrates to discriminate between changes in trophic position and changes in isotopic baseline levels, while ruling out the effect of fasting on these patterns. Analyses were conducted on samples extracted from two baleen plate segments: one corresponding to winter, another to summer. The trophic position was higher and slightly more variable in winter (3.6 ± 0.7) than in summer (3.0 ± 0.4), which indicates that during winter fin whales tend to feed on fish and are more generalist in feeding habits. Interestingly, the δ15NPhe values were not lower in winter than in summer (winter: 5.2‰ ± 2.4‰; summer: 4.0‰ ± 2.1‰). This was unexpected because baseline δ15N values (e.g., zooplankton) tend to be lower at low latitudes, where fin whales are believed to spend the winter. Fin whales may remain in relatively high latitudes during winter or visit low‐latitude areas with locally higher than average δ15N values, such as upwelling areas. [ABSTRACT FROM AUTHOR]

Rationale: Stable isotope analysis of growth layers in sperm whale teeth dentine can provide valuable insight into individual long‐distance displacements and diet. Although treating teeth half‐sections with formic acid and rubbing their surface with a graphite pencil improves growth layer visibility and reduces sampling error, previous studies mostly used untreated half‐sections as the effect that this treatment may have on stable isotope ratios in dentine is unknown. The present study investigates the treatment effect on stable C and N isotope ratios in sperm whale teeth dentine. Methods: In the teeth of 30 sperm whales, we analysed and compared samples of powdered dentine obtained from (a) untreated half‐sections, (b) half‐sections etched with formic acid and rubbed with a graphite pencil and (c) half‐sections etched with formic acid from which the graphite pencil rubbing had been cleansed off. δ13$$ {\delta}^{13} $$C and δ15$$ {\delta}^{15} $$N values were compared between the three sample groups. Results: We found significant differences in values of both elements between untreated and etched samples, with a mean increase of 0.2% in δ13C and δ15N values in the etched samples. No significant differences were found between etched samples with graphite rubbing versus those without it. Significant linear regression models were calculated to predict untreated δ13C and δ15N values from the values obtained in the etched half‐sections with limited precision. Conclusions: We show for the first time that formic acid etching has a clear effect on δ13$$ {\delta}^{13} $$C and δ15$$ {\delta}^{15} $$N values in sperm whale teeth dentine. The developed models permit the estimation of untreated values from etched half‐sections, thus enabling the use of the latter in stable isotope analysis. However, as treatment procedures may vary between studies, it is advisable that similar predictive models are developed case‐by‐case to ensure comparability of results. [ABSTRACT FROM AUTHOR]

The Gulf of Ambracia, in northwestern Greece, hosts a highly threatened community of about 150 common bottlenose dolphins (Tursiops truncatus). Until now, information on their feeding habits was derived exclusively from fish scale samples collected during surface‐feeding events targeting small schooling epipelagic fish. The aim of this study was to determine the diet of bottlenose dolphins living in the Gulf of Ambracia through the application of Bayesian isotopic mixing models. Skin biopsy samples of 16 dolphins were analyzed and no difference related to sex or age‐class was found in δ13C and δ15N values. Results suggested that the dolphin diet was mainly based on Trachurus trachurus, species belonging to the family Sparidae: Diplodus annularis, Lithognathus mormyrus, and Sepia officinalis, which represented together about 42% ± 15% of the biomass ingested, followed by species belonging to the order Clupeiformes (Engraulis encrasicolus, Sardinella aurita, and Sardina pilchardus) and the genus Gobius (37% ± 17%). A better understanding of the feeding habits of these dolphins sheds light on the feeding ecology of this highly threatened population by, for instance, evidencing interactions with artisanal fisheries sharing the same target species, and is key for identifying adequate management measures consistent with an ecosystem‐based approach. [ABSTRACT FROM AUTHOR]

The fish‐eating, type‐C ecotype, killer whale is a top predator in the Ross Sea, Antarctica. Increasing knowledge of this animal's foraging habitats, diet and movement patterns is listed amongst the research priorities adopted under the framework of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR).To contribute to this goal, satellite transmitters were deployed on 10 type‐C killer whales and skin biopsies were obtained from seven individuals in Terra Nova Bay (Ross Sea) during austral summer (January–February) 2015. Hierarchical switching state–space models (hSSSM) were applied to Argos satellite tracking data to describe the movements of tagged whales, which were then paired with available diving data. Stable isotopes analyses were performed on the biopsy samples to describe the diet.A total of 8,803 Argos locations were available to fit the hSSSM. All whales engaged in potential foraging activity in localized areas along the Ross Sea coastline, followed by uninterrupted travel (i.e. migration) outside Antarctic waters, with no evidence of foraging activity. The pattern of deeper dives matched the occurrence of encamped behaviour indicated by the hSSSM results. The stable isotopes analysis indicated that Antarctic toothfish comprised the largest component (35%) of the prey biomass, raising concerns since this species is targeted by commercial fishery in the Ross Sea Region.These results provide new insights into the ecology of type‐C killer whales in the Ross Sea Region, underlining a potential threat from commercial fishing in the area. Considering the recent establishment of the Ross Sea Region Marine Protected Area, these findings will contribute to the required Research and Monitoring Programme of the Marine Protected Area and provide new empirical evidence to inform conservation measures in the existing Terra Nova Bay Antarctic Special Protected Area. [ABSTRACT FROM AUTHOR]

Mediterranean monk seals (MMS) are among the most endangered marine mammals on Earth. We screened mitochondrial variability (control region [CR1] and mitogenomes) of the species through a 180‐yr timeframe and extended by 20% (n = 205) the number of samples from a previous investigation, including historical specimens from 1833 to 1975. Although we detected two new, rare CR1 haplotypes, genetic diversity remained extremely low. Fully resolved haplotype median network and rarefaction analysis both suggested low probability for further unscreened haplotypes. There was no clear phylogeographic structure across the 12 marine subdivisions covered by the species' range. Haplotypes previously considered diagnostic of the extant North Atlantic and eastern Mediterranean populations had their distributions extended into the western Mediterranean and the North Atlantic, respectively, by both historical and recent samples. Our study suggests that MMS have been genetically depauperate since at least the mid‐19th century, and that the massive 1997 die‐off in Western Sahara (North Atlantic) could have caused local haplotype extinctions. Our results support the hypothesis of past metapopulation dynamics across the species range, where the current segregation into geographically distant and genetically depauperate breeding populations (i.e., North Atlantic and eastern Mediterranean Sea) derives from the combined effects of historical extinctions, genetic drift on small breeding groups, and persistently low levels of genetic diversity. [ABSTRACT FROM AUTHOR]

In cetaceans, stable isotope analysis of tissues overcomes some of the potential biases encountered in studies of diet based on stomach content or fecal analysis. However, stable isotope ratios of tissues are only indicative of long‐term feeding and may be misleading when recent shifts in prey consumption have occurred. Stable isotope ratios of feces stand as a potential alternative source for resolving short‐term diet, but may be biased by digestive enzymes and bacteria. We investigate whether fecal stable isotope ratios of freshly dead fin whales are consistent with those of the main food found in their stomachs (krill) and with those of other potential prey. Results show that stable isotope ratios of krill remain unaltered after their transit along the digestive tract and, therefore, values in feces are reliable indicators of this prey consumption. In addition, the low isotope ratios of feces that visually appeared to contain only fish remains revealed a substantial contribution of krill in the digested food. This demonstrates that macroscopic gross fecal analysis may be misleading because less digestible components, like fish bones, may be overrepresented. We conclude that stable isotope ratios of feces contribute significant information to other techniques for short‐term diet reconstruction. [ABSTRACT FROM AUTHOR]

Rationale: Baleen plates are anatomical structures composed of inert tissue that hang from the upper jaw in mysticetes. Baleen plates may differ in size and in coloration between different segments of the filtering row or between sides of the mouth. Concern has been raised that variation in baleen plate characteristics may reflect dissimilar structural composition and growth rates liable to affect stable isotope ratios and their oscillation patterns. Methods: We measured stable carbon (δ13C values) and nitrogen (δ15N values) isotope ratios at intervals of 1 cm along the longitudinal axis of six baleen plates collected from different positions along the mouth of a fin whale. All samples were analysed using a continuous flow isotope ratio mass spectrometer. Generalized additive models were fitted to the data from each baleen plate and the results of the models were compared visually. Results: A total of 206 samples were analysed. Visually, all baleen plates presented nearly identical oscillations, independent of the position or the coloration of the baleen plate. However, the variation in δ13C and δ15N values occurring between the different baleen plates was higher in the segments of oscillations exhibiting steeper slopes. Conclusions: Differences in size between plates in an individual are due to differential erosion rates according to their position in the mouth. Therefore, the position of sampling along the baleen plate row should not be a reason for concern when conducting stable isotope studies. [ABSTRACT FROM AUTHOR]

Rationale: Isotope ratios from skin samples have been widely used to study cetacean trophic ecology. Usually, isotopic skin uniformity has been assumed, despite the heterogeneity of this tissue. This study aims to investigate (1) regional isotopic variation within the skin in cetaceans, and (2) isotopic variation among internal tissues. Methods: Stable carbon (δ13 C values) and nitrogen (δ15 N values) isotope ratios were measured in 11 skin positions in 10 common dolphins (Delphinus delphis) and 9 striped dolphins (Stenella coeruleoalba). In addition, the isotope ratios in the muscle, liver and kidney of both species were determined and compared with those from the skin and from all tissues combined. The signatures were determined by means of elemental analyser/isotope ratio mass spectrometry (EA/IRMS). Results: In both species, no differences between isotope ratios of the skin positions were found. Moreover, the isotope ratios of skin were similar to those of muscle. In contrast, liver and kidney showed higher isotope ratios than muscle and skin. Conclusions: Isotopic homogeneity within the skin suggests that the isotope ratios of a sample from a specific skin position can be considered representative of the ratios from the entire skin tissue in dolphins. This conclusion validates the results of previous stable isotope analyses in dolphins that used skin samples as representative of the whole skin tissue. Isotopic similarities or dissimilarities among tissues should be considered when analysing different tissues and comparing results from the same or different species. [ABSTRACT FROM AUTHOR]

The North Atlantic fin whale was subject to heavy exploitation in the past and, despite partial recovery, it is still considered endangered. Recent research has questioned its currently accepted subpopulation structure and migratory movements, challenging management and conservation efforts. Here we contribute to this discussion by presenting results of stable isotope analysis of fin whale bones and krill samples collected from fin whale stomachs from two exploited areas, west Iceland and northwest Spain, and comparing these results with North Atlantic isoscapes. In krill, δ15N values were highly variable and no significant differences in δ15N and δ13C between areas emerged. δ15N and δ13C values in bone were higher than in krill, due to trophic enrichment, and were not significantly different between areas. Both krill and bone results were slightly inconsistent with the local isoscapes, maybe due to seasonal variations in local productivity and in krill diet and, in the case of bone, to its capability to integrate long-term isotopic values, derived from food consumed in distant areas. Conversely, δ18O values, which reflect the basal signal of sea water, were consistent with isoscapes and significantly higher in whales from northwestern Spain, possibly indicating migration to breeding grounds located at lower latitudes. [ABSTRACT FROM AUTHOR]

The article discusses a study which investigates the genetic structure of harbour porpoise and its range of species distribution on western Palearctic waters. Topics discussed include the existence of three ecotypes of harbour porpoise, the impact of climate change on the pelagic predators' distribution and speciation, and the allopatric divergence involving highly mobile species.

RATIONALE The relationship between stocks of fin whales inhabiting the temperate eastern North Atlantic and the Mediterranean Sea is subject to controversy. The use of chemical markers facilitates an alternative insight into population structure and potential borders between stocks because the two areas present dissimilar isotopic baselines. METHODS Baleen plates, composed of inert tissue that keeps a permanent chronological record of the isotopic value of body circulating fluids, were used to investigate connectivity and boundaries between the stocks. Values were determined by continuous flow isotope ratio mass spectrometry. RESULTS Stable isotopes confirm that, while the two subpopulations generally forage in well-differentiated grounds, some individuals with characteristic Atlantic values do penetrate into the Mediterranean Sea up to the northernmost latitudes of the region. As a consequence, the border between the two putative subpopulations may be not as definite as previous acoustic investigations suggested. The discriminant function obtained in this study may assist researchers to use baleen plate isotopic data to assign the origin of fin whales of uncertain provenance. CONCLUSIONS This study strengthens the stock subdivision currently accepted for management and conservation while recognizes a low level of exchange between the Mediterranean and temperate eastern North Atlantic subdivisions. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article related to uncertain status of the Mediterranean and northeastern North Atlantic fin whale.