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Teeth of odontocetes accumulate annual dentinal growth layer groups ( GLGs) that record isotope ratios, which reflect the time of their synthesis. Collectively, they provide lifetime records of individual feeding patterns from which life history traits can be inferred. We subsampled the prenatal dentin and postnatal GLGs in Risso's dolphins ( Grampus griseus) ( n = 65) that stranded or were collected as bycatch in Taiwan (1994-2014) and analyzed them for δ15N and δ13C. Age-specific δ15N and δ13C values were corrected for effects of calendar year, stranding site, C/N, and sex. δ15N values were higher in prenatal layers (14.94‰ ± 0.74‰) than in adult female GLGs (12.58‰ ± 0.20‰), suggesting fetal enrichment during gestation. Decreasing δ15N values in early GLGs suggested changes in dietary protein sources during transition to complete weaning. Weaning age was earlier in males (1.09 yr) than in females (1.81 yr). Significant differences in δ15N values between weaned males and females suggest potential sexual segregation in feeding habits. δ13C values increased from the prenatal to the 4th GLG by ~1.0‰, indicative of a diet shift from 13C-depleted milk to prey items. Our results provide novel insights into the sex-specific ontogenetic changes in feeding patterns and some life history traits of Risso's dolphins. [ABSTRACT FROM AUTHOR]

The article examines the resting oxygen consumption rates of ex situ adult male killer whale (Orcinus orca) and obtain basal metabolic rate (BMR) measurements. It develops a functional methodology and employs it to measure the same. It is said that accurate measurement of BMR is the foundation of any bioenergetic model.

Diet-tissue discrimination factors (Δ15N or Δ13C) and turnover times are thought to be influenced by a wide range of variables including metabolic rate, age, dietary quality, tissue sampled and the taxon being investigated. In the present study, skin samples were collected from ex situ dolphins that had consumed diets of known isotopic composition for a minimum of 8 weeks. Adult dolphins consuming a diet of low fat (5-6%) and high &#94815N value had significantly lower Δ15N values than animals consuming a diet with high fat (13.9%) and low &#94815N value. Juvenile dolphins consuming a diet with low fat and an intermediate &#94815N value had significantly higher Δ15N values than adults consuming the same diet. Calculated half-lives for &#94815N ranged from 14 to 23 days (17.2±1.3 days). Half-lives for &#94813C ranged from 11 to 23 days with a significant difference between low fat (13.9±4.8 days) and high fat diets (22.0±0.5 days). Overall, our results indicate that while assuming a Δ13C value of 1‹ may be appropriate for cetaceans, Δ15N values may be closer to 1.5‹ rather than the commonly assumed 3‹. Our data also suggest that understanding seasonal variability in prey composition is another significant consideration when applying discrimination factors or turnover times to field studies focused on feeding habits. Isotope retention times of only a few weeks suggest that, in addition, these isotope data could play an important role in interpreting recent fine-scale habitat utilization and residency patterns. [ABSTRACT FROM AUTHOR]

Steller sea lion (Eumetopias jubatus) populations have undergone precipitous declines through their western Alaskan range over the last four decades with the leading hypothesis to explain this decline centering around changing prey quality, quantity, or availability for this species (i.e., nutritional stress hypothesis). Under chronic conditions of reduced food intake sea lions would conserve energy by limiting energy expenditures through lowering of metabolic rate known as metabolic depression. To examine the potential for nutritional stress, resting metabolic rate (RMR) and body composition were measured in free-ranging juvenile Steller sea lions (N = 91) at three distinct geographical locations (Southeast Alaska, Prince William Sound, Central Aleutian Islands) using open-flow respirometry and deuterium isotope dilution, respectively. Average sea lion RMR ranged from 6.7 to 36.2 MJ d−1 and was influenced by body mass, total body lipid, and to a lesser extent, ambient air temperature and age. Sea lion pups captured in the Aleutian Islands (region of decline) had significantly greater body mass and total body lipid stores when compared to pups from Prince William Sound (region of decline) and Southeast Alaska (stable region). Along with evidence of robust body condition in Aleutian Island pups, no definitive differences were detected in RMR between sea lions sampled between eastern and western populations that could not be accounted for by higher percent total body lipid content, suggesting that that at the time of this study, Steller sea lions were not experiencing metabolic depression in the locations studied. [ABSTRACT FROM AUTHOR]

Humpback whales are considered generalist predators, feeding on schooling fish, and zooplankton, but variability likely exists among regional feeding aggregations. We explored the diet of one feeding aggregation of humpback whales near Kodiak Island, Alaska, through analysis of the stable carbon (δ13C) and nitrogen (δ15N) isotope ratios of their skin and regional prey sources. Humpback whales were sampled during the summer feeding season over 3 yr ( n= 93; 2004-2006). Prey samples were collected from the same region during trawl surveys conducted between 2003 and 2005. Isotope values of humpback whale skin and prey were entered into a Bayesian dietary mixing model to estimate feasible contributions of prey to humpback diets. Diet results indicated that humpbacks feed heavily on euphausiids, but also consume juvenile walleye pollock, capelin, and Pacific sand lance. The diet of humpback whales in 2004 was the most diverse, while diets in 2005 and 2006 showed a higher proportion of euphausiids. Our results reveal annual differences in humpback diets from the Kodiak region due to either individual prey preferences or prey availability. Application of a Bayesian mixing model to stable isotope analysis improves description of regional diets and comparison of these diets to resource availability and quality. [ABSTRACT FROM AUTHOR]

Trophic levels of 1,105 humpback whales from six geographically and isotopically distinct North Pacific feeding groups were calculated using δ15N of humpback whales and regional primary consumers. The overall mean trophic level for North Pacific humpback whales was 3.6 ± 0.02, indicating a diet of both fish and zooplankton, and, thus, supporting assumptions of humpback whales as generalist predators. The highest mean trophic level was calculated for the north Gulf of Alaska group (4.0 ± 0.03), while the lowest was found for the Russian and the western Aleutian Islands group (3.3 ± 0.08). Differences in mean trophic levels suggest that feeding groups differ in the proportion of fish and zooplankton in their diets. [ABSTRACT FROM AUTHOR]

Odontocete blubber has been shown to be variable in composition and can be separated into strata visually, histologically, and biochemically. The purpose of this study was to examine fatty acid composition of bottlenose dolphin (Tursiops truncatus (Montagu, 1821)) blubber, and determine if differences exist between body sites, reproductive states, and (or) seasons. The influence of these variables on blubber composition could aid in the creation of a model that would use fatty acid signature analysis to evaluate diet in free-ranging populations. Blubber samples were obtained from freshly dead animals along the Texas and Louisiana coastlines. Samples from nine body sites were analyzed to investigate site variability, and from one site to evaluate differences due to season, reproductive state, and blubber layer. All body sites of animals sampled in the winter were statistically indistinguishable, indicating that biopsy samples could be obtained from any location on the animal for fatty acid analysis during this season; however, three distinct blubber layers were identifiable, and reproductive states were significantly different in terms of fatty acid composition. Seasonal differences in fatty acid composition were also highly significant for all one-site inner blubber layer samples. Ultimately, the differences in fatty acid composition could have resulted from dietary or physiological factors and need to be examined further. [ABSTRACT FROM AUTHOR]

We investigated the feeding ecology and foraging location of migrating and nursing northern fur seal (Callorhinus ursinus) adult females and migrating juvenile males from the Pribilof Islands, Alaska, using carbon (δ13C) and nitrogen (δ15N) isotope analysis of fur seal skin and whole potential prey. Post-parturient and lactating females had mean δ15N values significantly (0.8‰) higher than pregnant, migratory females, and δ13C values that were not significantly different. Two opportunistically collected, migrating, nulliparous females had mean δ13C values 1.1‰ lower than migrating, pregnant females, and δ15N values that were not different. Pregnant, migratory females had mean δ13C values significantly (~1.5‰) higher than migratory juvenile males, and mean δ15N values significantly (~0.6–1.6‰) higher than migratory juvenile males. The exception was one group of juvenile males from St. Paul Island with mean δ15N values that were not significantly different from migrating females. The mean δ15N values of pregnant females indicate they were feeding at a higher trophic level than juvenile males during migration. The higher mean δ13C values for pregnant females suggest they were feeding coastally during the spring migration, while juvenile males and nulliparous females were feeding offshore. The higher δ15N values for post-parturient, lactating females over migrating, pregnant females point to either a trophic shift in diet over time, or a more likely 15N-enrichment due to negative nitrogen balance caused by the nutritional stress of lactation and the feeding/fasting regime experienced by females. Similar mean δ13C values for migrating and breeding-season females indicate that both groups were feeding in coastal, on-shelf domains during their respective time periods. Similar mean δ15N values for nulliparous and pregnant females indicate they were feeding at similar trophic levels despite indications of feeding in separate ecosystems during migration. Using a δ15N shift of 2–3‰ per trophic level, we made general inferences about the trophic levels at which northern fur seals were feeding. The interpretation of our δ15N data indicates that migrating pregnant females, lactating females and the majority of migrating juvenile males consumed prey with mean δ15N values between 14.2‰ and 15.2‰, 15.1‰ and 16.1‰, and 13.6‰ and 14.6‰, respectively. Probable fur seal prey was analyzed as well. Walleye pollock showed progressive 15N and 13C-enrichments with age. Mean δ15N and δ13C values of 3- to 4-year-old fish were ~6.0‰ and 1.1‰ higher, respectively, than values for 0-age pollock. Atka mackerel also showed isotopic enrichment with age. The δ15N and δ13C values of large fish were 0.8‰ and 0.3‰ higher, respectively, than values for smaller fish. [ABSTRACT FROM AUTHOR]

Describes the presence of amphipod Isocyamus delphinii in the carcass of melon-headed whale Peponocephala electra. Cetacean hosts of the amphipod parasite; Number of cyamid amphipods recovered from the lesions; Information on the body lengths of the amphipods; Factor that contributes to the interspecific host transmission of the parasite.

Steller sea lion (Eumetopias jubatus) populations have undergone precipitous declines through their western Alaskan range over the last four decades with the leading hypothesis to explain this decline centering around changing prey quality, quantity, or availability for this species (i.e., nutritional stress hypothesis). Under chronic conditions of reduced food intake sea lions would conserve energy by limiting energy expenditures through lowering of metabolic rate known as metabolic depression. To examine the potential for nutritional stress, resting metabolic rate (RMR) and body composition were measured in free-ranging juvenile Steller sea lions (N = 91) at three distinct geographical locations (Southeast Alaska, Prince William Sound, Central Aleutian Islands) using open-flow respirometry and deuterium isotope dilution, respectively. Average sea lion RMR ranged from 6.7 to 36.2 MJ d−1 and was influenced by body mass, total body lipid, and to a lesser extent, ambient air temperature and age. Sea lion pups captured in the Aleutian Islands (region of decline) had significantly greater body mass and total body lipid stores when compared to pups from Prince William Sound (region of decline) and Southeast Alaska (stable region). Along with evidence of robust body condition in Aleutian Island pups, no definitive differences were detected in RMR between sea lions sampled between eastern and western populations that could not be accounted for by higher percent total body lipid content, suggesting that that at the time of this study, Steller sea lions were not experiencing metabolic depression in the locations studied. [ABSTRACT FROM AUTHOR]

An unusual mortality event (UME) was declared for cetaceans in the northern Gulf of Mexico (GoM) for Franklin County, Florida, west through Louisiana, USA, beginning in February 2010 and was ongoing as of September 2014. The 'Deepwater Horizon' (DWH) oil spill began on 20 April 2010 in the GoM, raising questions regarding the potential role of the oil spill in the UME. The present study reviews cetacean mortality events that occurred in the GoM prior to 2010 (n = 11), including causes, durations, and some specific test results, to provide a historical context for the current event. The average duration of GoM cetacean UMEs prior to 2010 was 6 mo, and the longest was 17 mo (2005-2006). The highest number of cetacean mortalities recorded during a previous GoM event was 344 (in 1990). In most previous events, dolphin morbillivirus or brevetoxicosis was confirmed or suspected as a causal factor. In contrast, the current northern GoM UME has lasted more than 48 mo and has had more than 1000 reported mortalities within the currently defined spatial and temporal boundaries of the event. Initial results from the current UME do not support either morbillivirus or brevetoxin as primary causes of this event. This review is the first summary of cetacean UMEs in the GoM and provides evidence that the most common causes of previous UMEs are unlikely to be associated with the current UME.

Sixty-five fatty acids were quantified in the blubber of common dolphins (Delphinus delphis, D. capensis) incidentally caught off the coast of southern California. Dolphins were grouped by sex, reproductive status and species, and a blubber sample was collected at a mid-lateral site located caudal to the trailing edge of the dorsal fin. Samples were divided horizontally into inner, middle and outer layers and gradients in fatty acid content (mass percent) were observed across the depth of the blubber. Levels of monounsaturated fatty acids were greatest in the outer layer, whereas levels of saturated and polyunsaturated fatty acids were greatest in the inner layer. Degree of stratification was greatest in sexually mature dolphins. Blubber of sexually immature, but physically mature, male dolphins was also highly stratified, suggesting that this difference may be attributed to differences in diet. Classification and regression tree analysis resulted in the fewest misclassifications when dolphins were grouped by species, possibly indicating that these closely related animals forage on different prey species. Dietary-derived fatty acids were typically selected as splitting criteria in classification and regression tree analyses, suggesting that the observed differences in fatty acid composition between the various groups of dolphins may be attributed to differences in diet.