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The lipid and fatty acid (FA) composition of the outer blubber layer was characterized in 46 east Australian migrating humpback whales Megaptera novaeangliae. Samples were obtained at 2 time points of the annual migration, which occurs between Antarctic feeding grounds and low-latitude breeding grounds and is associated with a prolonged period of fasting. Blubber lipid composition was dominated by triacylglycerols in all individuals, and the FA profiles of both migration cohorts and sexes were dominated by monounsaturated fatty acids (MUFA). Results indicate that males primarily mobilise polyunsaturated fatty acids in response to migration and fasting, favouring the most readily utilisable FA as governed by their physicochemical properties. In comparison, females appear to initially mobilise short-chain (

This study was performed to evaluate the stability of the fatty acid (FA) composition of blubber from Baltic grey seals Halichoerus grypus archived at −25°C in the Swedish Environmental Specimen Bank (SESB). Possible alterations of FA compositions with storage time and temperature were evaluated. Blubber from 5 seals was kept at +2°C and at −20°C and sampled for up to 6 mo and 33 mo, respectively. Furthermore, FA profile stability was evaluated in blubber stored in the SESB for 4 and 6 yr. This was done by re-sampling and re-analyzing blubber samples from SESB. In both parts of the study, a principal component analysis was performed on 48 FAs comprising 98 to 99% of the total FAs in blubber of Baltic grey seals. We found no indication of a critically altered FA composition, neither in blubber stored at +2°C for 6 mo nor in blubber stored at −20°C for 33 mo. The re-analysis of samples stored in SESB for ~4 to 6 yr only differed for a few FAs in some samples. The most remarkable differences were a slight increase in some long-chain unsaturated FAs (18:2n-6, 20:3n-3, 20:4n-3, 22:4n-3). As an increase in long-chain polyunsaturated FAs due to storage is highly unlikely, we believe that this is probably more due to the sampling technique than to a critically altered FA composition due to storage. Our results suggest that archived seal blubber may be safely used in retrospective analyses of diet using an FA signature analysis technique.

The high variability in reproductive performance of North Atlantic right whales Eubal- aena glacialis compared to southern right whales Eubalaena australis may reflect differences in lipid reserves. Amplitude-mode ultrasound was used to measure the thickness of right whale integument (epidermis and blubber, herein referred to as blubber thickness) in E. glacialis in the Bay of Fundy, Canada for 5 summer seasons and in E. australis off the South African coast for 2 austral winter sea- sons. E. glacialis had significantly thinner blubber layers (mean ±1 SD = 12.23 ± 2.16 cm, n = 172) than E. australis (16.13 ± 3.88 cm, n = 117), suggesting differing levels of nutrition between the 2 species. Blubber was thickest in females measured 3 to 6 mo prior to the start of pregnancy (E. glacialis), thin- ner during lactation (E. glacialis, E. australis) and then thicker with time after weaning (E. glacialis). These results suggest that lipids in blubber are used as energetic support for reproduction in female right whales. Blubber thickness increased in calves during suckling (E. glacialis, E. australis) but sub - sequently decreased after weaning (E. glacialis). Juvenile and adult male E. glacialis blubber thick- nesses were compared between years of differing prey Calanus finmarchicus abundances (data from Pershing et al. 2005; ICES J Mar Sci 62:1511-1523); during a year of low prey abundance whales had significantly thinner blubber than during years of greater prey abundance. Taken together, these re- sults suggest that blubber thickness is indicative of right whale energy balance and that the marked fluctuations in North Atlantic right whale reproduction have a nutritional component.

The predator–prey relationship with respect to fatty acids (FAs) was studied in 57 harp seals Pagophilus groenlandicus and 16 potential prey species collected simultaneously in the northwestern Barents Sea in May–June 2006. The FA composition of potential prey and the inner and outer sections of the seal blubber was determined. The blubber was stratified with a higher abundance of monounsaturated FAs (14 to 18 carbons) in the outer layer and a higher abundance of saturated FAs and monounsaturated long-chain FAs (20 to 24 FAs) in the inner layer. The FA composition differed substantially among potential prey species and between the prey and the blubber. The FA composition of the prey species, which was identified from stomach and/or intestine contents, was more similar to that of the blubber than that of the prey not found in the stomach or intestines. The FA composition of the outer blubber layer was independent of prey composition but dependent on the age of the seals. The weak predator–prey relationship with respect to FA composition of the inner blubber and the prey suggested that the FA composition of the inner layer was mainly predetermined by metabolism rather than the FA composition of the diet. Thus, using blubber FA composition as an estimation of prey use appears unreliable. 2016-03-28

The ability to determine the age of individual humpback whales Megaptera novaeangliae and estimate population age distributions is fundamental to assessments of status and long-term viability. Existing methods of ageing large whales rely either on limited longitudinal sighting studies of individual whales from their year of birth, or on post-mortem procedures to extract tissues suitable for determining age. Here we describe a potential method for ageing live free-ranging humpback whales using low-impact biopsy sampling techniques. Shallow outer-blubber samples were obtained from known-age whales from 2 distinct populations (North Atlantic, Gulf of Maine, n = 39; North Pacific, Southeast Alaska, n = 31), and analyzed for their fatty acid (FA) compositions. Multilinear FAage models were derived for these known-age whales, and serve as the basis from which the age of unknown-age whales can be estimated. Four FA-age models were developed; one for each humpback population analyzed separately, and an additional 2 by combining both populations into a single dataset and deriving models based on ‘exact’ and ‘exact’ plus ‘minimum’ known-age whales independently. Each of these empirical models was based on a linear combination of 2 FA ratios rather than individual FA compositions, and shown to be largely independent of sex, diet and nutritional status. Although the precision (σ) of these models was somewhat variable (ranging between 3.1 and 5.3 yr for the specific populations modeled), the results suggest that it may be possible to estimate the age of individual humpback whales from any population with better than decadal resolution using this approach.

When resources are limited or patchy, a species may develop some degree of resource partitioning to reduce intra-specific competition. Development of intra-specific resource partitioning is more pronounced in species with clear phenotypic variation among individuals (e.g. age or sex). Southern elephant seals Mirounga leonina have pronounced sexual dimorphism and range widely in size and foraging range between juvenile and adult stages. However, hypothesized diet-based resource partitioning has been less clear due to difficulties in sampling diet while seals are away from breeding islands. We analysed fatty acids (FAs) from blubber of 122 juvenile seals and compared them to FA profiles from blubber of 52 adult females, and to FA profiles from 51 prey species (grouped as fish and squid) to examine evidence for diet-based resource partitioning in the seals. FA signature analysis revealed physiological and dietary differences between ages. Principle components of the 21 FAs from seal blubber and prey parts distinguished prey from seals, and clearly separated prey species into fish and squid classes. FA profiles from adult females differed to those from juveniles, with the former more 'squid-like' and the latter more 'fish-like'. Variation in FA profiles of seals was also apparent between sexes and during different seasons. Differences in diet between juveniles and adult females suggest resource partitioning occurs in response to large metabolic and physiological differences with age that limit juvenile dispersal and diving abilities. By consuming a different suite of prey species relative to adult females, juvenile southern elephant seals may reduce intra-specific competition.

Knowledge of the age distributions of killer whale Orcinus orca populations is critical to assess their status and long-term viability. Except for accessible, well-studied populations for which historical sighting data have been collected, currently there is no reliable benign method to deter- mine the specific age of live animals for remote populations. To fill this gap in our knowledge of age structure, we describe new methods by which age can be deduced from measurements of specific lipids, endogenous fatty acids (FAs) and FA ratios present in their outer blubber layers. Whereas cor- relation of wax and sterol esters with age was reasonable for female 'resident' killer whales, it was less well-defined for males and 'transients.' Individual short-, branched-, and odd-chain FAs corre- lated better with age for transients and residents of both sexes, but these single parameter relation- ships were population specific and seemingly varied with long-term diet. Alternatively, a simple, empirical multi-linear model derived from the combination of 2 specific FA ratios enabled the ages of individual eastern North Pacific killer whales to be predicted with good precision (σ = ±3.8 yr), appeared to be independent of individual diet and was applicable to both genders and ecotypes. The model was applied to several less well-studied killer whale populations to predict their age distribu- tions from their blubber FA compositions, and these distributions were compared with a population of known age structure. Most interestingly, these results provide evidence for the first time that adult male transient killer whales appear to have lower life expectancies than do their resident counter- parts in Alaska.

Quantitative fatty acid (FA) signature analysis (QFASA) has recently been developed to estimate the species composition of predator diets by statistically comparing FA signatures of preda- tor adipose tissue with that of their potential prey. Captive feeding trials were used to further test the technique with newly weaned harbour seals Phoca vitulina richardsi (N = 21). Two groups of seals were fed monotypic diets of either Pacific herring Clupea pallasii or surf smelt Hypomesus pretiosus for 42 d while a third group was fed smelt for 21 d followed by herring for 21 d. Blubber biopsies were taken dorsally at Days 0, 21 and 42. Specific calibration coefficients (CC) used by QFASA were devel- oped from 4 juvenile harbour seals and in some cases differed by 2-fold with previously reported phocid CC values. The QFASA diet estimates were evaluated using 2 CC sets, 15 FA subsets and a library of 3 to 11 potential prey species. Diet switches were best tracked using the harbour seal CC and the new FA subset. Overall prey misclassifications were apparent (mean = 12%, range = 4 to 25%) when modeled with 8 additional prey not fed, a trend consistent with overlapping prey FA signatures. Blubber FA turnover rates were not strictly linear and in the order of 1.5 to 3 mo in newly weaned seals. Following parameter optimization of the model, QFASA estimates reflected major diet trends in the feeding study, but were sensitive to the CC and FA subsets used as well as to prey spe- cies with similar FA signatures. Our results have important implications in the application of QFASA to the study of pinniped diets with more complex feeding histories and wider prey fields.

Blubber fatty acid (FA) profiles of young Steller sea lions Eumetopias jubatus (

Blubber biopsy samples from eastern North Pacific killer whales Orcinus orca were ana- lyzed for fatty acids, carbon and nitrogen stable isotopes and organochlorine contaminants. Fatty acid profiles were sufficiently distinct among the 3 reported ecotypes ('resident,' 'transient' or 'offshore') to enable individual animals to be correctly classified by ecotype and also by mitochondrial DNA (mtDNA) haplotype. Profiles of PCBs also enabled unambiguous classification of all 3 killer whale ecotypes, but stable isotope values lacked sufficient resolution. Fatty acid, stable isotope and PCB profiles of the resident and transient ecotypes were consistent with those expected for these whales based on their reported dietary preferences (fish for resident whales, marine mammals for transients). In addition, these ecotype profiles exhibited broad similarity across geographical regions, suggesting that the dietary specialization reported for resident and transient whales in the well-studied eastern North Pacific populations also extends to the less-studied killer whales in the western Gulf of Alaska and Aleutian Islands. Killer whales of the same ecotype were also grouped by region of sample col- lection. The mean stable isotope ratios of various regional groups differed considerably, suggesting that the prey preferences of these North Pacific killer whales may be both region and ecotype spe- cific. Furthermore, 3 specific ecotypes of killer whales were found to have measured stable isotope values that were consistent with dietary preferences reported in the literature. Finally, although the offshore population had blubber fatty acid profiles implicating fish as its primary prey, contaminant and stable isotope results were equally congruent with predation on marine mammals.

The fatty acid (FA) composition was determined in the blubber of 5 adult Baikal seals Phoca sibirica caught in July 2001, nine 1-mo old pups caught in April 2002, and 25 adults and fetuses from 3 of these, caught in October 2002, all along the SE shores of Lake Baikal, eastern Siberia. For comparison, FA in the blubber of ringed seals P. hispida, the closest marine relative of the Baikal seal, caught along the ice edge around Svalbard during 1999 and 2000 were also analyzed. The FA of the main prey of the Baikal and ringed seals, the endemic golomyanka Comephorus baikalensis and polar cod Boreogadus saida, respectively, were also studied. The same suite of FA was found in all samples. Saturated FA (SFA) with branched chains, all n6 polyunsaturated FA (PUFA) and 18:3n3 and 20:3n3 were more abundant in the blubber of the Lake Baikal seal and in the golomyanka than in the blubber of the marine ringed seal and marine fishes. In contrast, the relative levels of mono- unsaturated FAs (MUFA) with 20 and 22 carbons and polyunsaturated 20:5n3 were lower in the Baikal species than in the Svalbard species. The FA composition of the inner blubber was signifi- cantly different from the FA composition of the outer blubber in both species. Despite large differ- ences in FA composition between Baikal and ringed seal blubbers, vertical differences were mani- fested in the same FA: MUFA with 14, 16 and 18 carbons were present in higher relative abundance in the outer than in the inner layer. In both species all the other quantitatively important FA had lower or equal relative values in the outer layer. The FA composition of the seals' blubber differed from that of their main prey. The difference was, however, smaller between prey and inner blubber than between prey and outer blubber. The FA composition of the inner blubber of adults showed tempo- ral differences. Since the change from prey to blubber in relative concentration occurred in the same direction for all but 5 FA, the selection of FA during deposition in the inner blubber was similar for the 2 species, even though there was a large difference between the general FA composition of the freshwater and marine lipids. The FA composition in the blubber of adults, pups and fetuses differed.

There is growing concern about the health status of the harbour porpoise Phocoena phocoena in the North Sea and adjacent areas. The interaction between toxicological results (Zn, Cd, Cu, Fe, Se, Hg), stable isotope data (d13C and d15N) and the most common pathological findings, namely emaciation and lesions of the respiratory system, were investigated in 132 porpoises collected along the coasts of northern France, Belgium, Germany, Denmark, Iceland and Norway between 1994 and 2001. The body condition of harbour porpoises stranded on the French, Belgian and German coasts was poor compared to that of by-catch individuals from Iceland and Norway, as reflected by blubber thickness and hepatic to total body-mass ratio. High Zn and Hg concentrations were observed in some porpoises collected along the southern North Sea coast compared to by-catch individuals from Iceland, Norway and the Baltic Sea. Increasing Zn levels were observed with deteriorating health condition (emaciation and bronchopneumonia), while Hg increases were not significant. The increases were not related to shrinking liver mass which remained unchanged. These observations indicate a general redistribution of trace metals within the organs (muscles and blubber to liver), as a result of protein and lipid catabolism. Muscle d13C and d15N values remained unchanged with deteriorating body condition. Cd concentrations were associated only with age and low d15N values, indicating that high Cd concentrations in Iceland and Norway porpoises may be partly diet-related, i.e. a result of Cd contaminated prey.

Exposure to organochlorines induces retinoid deficiency in mammals; hence, retinoids are potential biomarkers of the impact of these pollutants. Appropriate target tissues to monitor retinoids in cetaceans have not been properly identified because of a lack of information on the con- tribution of each tissue to total body retinoids. Therefore, we have addressed this issue by studying the contribution of the main body tissues to retinoids in 21 common dolphins obtained from inciden- tal catches and in apparent good health and nutritive condition. Although concentrations in the liver were highest, those in blubber were also high and accounted for 43% of the total retinoid load of the compartments examined. As blubber can be obtained using non-invasive biopsy techniques, this tissue is proposed as a reliable indicator of retinoid status in cetaceans. However, blubber topo- graphical variation in structure and composition requires standardization of sampling sites. Retinoid concentrations did not differ significantly between sexes or with body size for any of the tissues, but the lipid content of blubber strongly influenced these concentrations. Biopsies from healthy, free- ranging individuals are preferred to samples from stranded animals. Further research on the in- fluence of factors (age, sex, reproductive condition, diet) that potentially affect retinoid levels is required to implement the use of retinoids as biomarkers of pollutant exposure in cetaceans.

PCB contamination was measured in the milk and serum of grey seal Halichoerus grypus mothers and in the serum of their pups sampled from 2 to 5 times between parturition and weaning on the Isle of May, Scotland, in 1998 and 2000. Blubber biopsies were also taken from the lactating females at early and late lactation in 2000. Concentrations of PCBs in milk stayed constant during the first part of lactation (0.31 +/- 0.17 mug g milk(-1)) and then increased at late lactation (0.67 +/- 0.42 mug g milk(-1)). Curiously, it did not follow the changes of milk lipid content, which increased at early lactation and then stayed constant until the end of the nursing period. As a result, even when expressed per unit of milk lipids, PCBs underwent a rise at the end of lactation. The changes in milk PCBs were accompanied by similar dynamics in maternal serum as well as in pup serum. Increased concentrations of PCBs at late lactation in serum and milk may be explained in part by the changes observed in maternal blubber. PCB levels increased significantly between early and late lactation in inner blubber, suggesting that PCBs are less easily mobilised from blubber than lipids. At late lactation, the retention capacity of the reduced blubber layer for PCBs might have reached its maximum. The mobilization of less polar lipids from blubber might also occur at this stage. In both cases, this could result in a higher mobilization of PCBs at this time. While inner blubber was significantly less concentrated than outer blubber at early lactation (1.26 +/- 0.72 mug g lipids(-1) in inner blubber vs 3.16 +/- 1.34 mug g lipids(-1) in outer blubber), these variations disappeared at late lactation (3.24 +/- 2.60 mug g lipids(-1) in inner blubber vs 3.59 +/- 1.46 mug g(-1) lipids in outer blubber). Newborn pups already had significantly higher serum levels of PCBs than their mothers, revealing an important placental transfer (11.9 +/- 7.0 ng ml serum(-1) in pups vs 6.7 +/- 3.5 ng ml serum(-1) in mothers). These differences were even greater in late lactation, due to the ingestion of milk (27.9 +/- 18.1 ng ml serum(-1) in pups vs 12.2 +/- 7.2 ng ml serum(-1) in mothers). As lactation progressed, PCB levels in pup serum increased exponentially as compared to the levels in the serum of their mothers.

The composition of the PCB mixture which is transferred from mother to pup in grey seals Halichoerus grypus throughout lactation was measured in the successive compartments of transfer: maternal blubber, maternal serum, milk and pup serum. Mother-pup pairs were captured regularly between birth and weaning on the Isle of May, Scotland. The PCB profiles of the different compartments of transfer consisted mainly of congeners 153, 138, 180, 187, 170 and 101, which made up 85% of the total PCB burden. Outer blubber contained higher relative concentrations (R-153) Of hepta-, octa-, and nona-chlorinated congeners (higher chlorinated congeners) than inner blubber, at both early (less than or equal to 5 d) and late (greater than or equal to 11 d) lactation. There was no change in the composition of the outer blubber layer between early and late lactation, while in the inner blubber, there was a slight increase in the R153 of higher chlorinated congeners at late lactation. In maternal serum, profiles changed towards having a higher proportion of higher chlorinated congeners as lactation progressed, but in milk, the PCB pattern stayed constant throughout lactation. Surprisingly, in pup serum profiles also changed towards higher R153 of higher chlorinated congeners at late lactation compared to early lactation, which was different to the pattern observed in milk. In all body compartments, higher proportions of higher chlorinated congeners were associated with higher concentrations of total PCBs. Maternal blubber and pup serum contained a higher R153 of higher chlorinated congeners than milk and, to a lesser extent, maternal serum. Thus biomagnification of the higher chlorinated congeners was recorded in pup serum.

Diet, and how it varies in place and time, are important factors in understanding the interactions between seals and fisheries. The grey seal eats a wide variety of prey species and varia- tions in availability of prey can lead to changes in both foraging behaviour and diet that could affect the ecological impact of the seals. Since it is difficult to observe the feeding behaviour of seals directly, we have used changes in the fatty acid profiles of blubber to indicate changes in their diet. We studied inter-colony and inter-annual variations in the fatty acid profiles of female seals from 2 Scottish breeding colonies, North Rona (RON) and the Isle of May, over 3 consecutive years from 1996 to 1998. The fatty acid profiles obtained were compared and tested using several multivariate statis- tical methods, including a new inter-population measure Dfap (a distance measure based on fatty acid profiles). There were significant inter-colony differences in blubber fatty acids in all years of the study. There were significant within-colony variations among years for the seals at the Isle of May but not at RON. Individual seals sampled in more than 1 yr tended to change in a similar manner at the Isle of May but not at RON. Discriminant analysis of the fatty acid profiles provided classifications of the Isle of May seals according to year with 84 to 97% accuracy, but was less successful with the RON seals with 56 to 74% accuracy. Only 4 out of 166 seals were 'mis-classified' into the wrong Isle of May or RON grouping. This analysis suggested a shift in diet at the Isle of May that was supported by evidence from a separate study on the analysis of otoliths in seal faeces.

Polar bears Ursus maritimus are predators of phocid seals, but they also forage oppor- tunistically on a variety of other species. In the Barents Sea — Svalbard area, their diet is thought to consist almost exclusively of ringed seals Phoca hispida, bearded seals Erignathus barbatus and harp seals P. groenlandica. When a seal is killed, polar bears preferentially consume the blubber. The fatty acid (FA) compositions of the outer, middle and inner adipose layer of 18 polar bears were compared to each other and also with the FA composition of the blubber of their prey, represented by 10 ringed seals, 10 harp seals and 9 bearded seals. The composition of the FAs in the inner layer of the bear adi- pose tissue differed from the composition of the outer layer, and was also distinctly different from the composition of the blubber from the prey. Fifteen of the 28 FAs analysed were found in lower relative amounts in the polar bears than in any of the 3 seal species. Eight of the FAs were found in higher rel- ative amounts in polar bears when compared to the 3 prey species. Only 5 of the FAs in polar bears were within the range of relative values found in the prey. This strongly suggests that polar bear adi- pose tissue has a unique FA composition that is not a straightforward mixture of what they consume, but rather is the result of selective processes prior to and during deposition of lipids in the tissue.

Pinnipeds have marked seasonal changes in body condition, accumulating energy re- serves prior to the reproduction period, and depleting these reserves during the breeding and molt- ing periods. This cycle is not well described in male harp seals Phoca groenlandica. We obtained mor- phometric measurements for 3167 Northwest Atlantic male harp seals sampled between 1979 and 1995. The part of the yearly cycle covered in this study (November to May) was divided into short blocks around median dates called 'periods'. For each period, a growth curve was calculated for body mass, sculp mass, core mass and standard length. These sequential growth curves were used to cal- culate changes in size-at-age between periods. In addition, seasonal changes in 3 condition indices (general, sculp and core condition), in blubber thickness and in the ratio of sculp to total mass were analyzed using locally weighted regressions. Male harp seals returned from their high-latitude feed- ing grounds heavier, in better condition, and with a thicker blubber layer than when they left the area in the spring. However, maxima in length, mass, condition and blubber thickness were not observed until the February 22 period (February 12 to March 4), or in the case of seals younger than 5 yr, some- time in March. Mass losses associated with the rut began between the periods February 22 and March 15 (March 5 to 25) and were most pronounced in seals older than 10 yr. About 66% of the losses in mass came from the core during this period. We estimated that males lost 39.4 kg during the rut (1.16 kg d -1 or 0.78% of initial mass d -1 , 44% from sculp and 56% from core) and incurred energy expenditures of 840 MJ (24.7 MJ d -1 ). This corresponds to twice the standard metabolic rate (SMR), and suggests that males are feeding during the rut. All males lost mass in April, and again in May. They began to molt April 19 period (April 16 to 22). Fewer than half the seals had completed the shed- ding of old hair when the study ended, in the May 10 period. Rates of mass loss during the molt varied from 1 to 1.8 kg d -1 , depending on the age of the seals. Minima of length, mass, condition and blubber thickness were observed in May. Molting appears to be a period of high energy expenditures (3 to 5 SMR) despite the low levels of activity observed at this time. This study revealed that length also changes seasonally: fat seals in February were longer than lean seals of the same age in late April.

We investigated changes in trophic level and feeding location over time in juvenile male northern fur seals Callorhinus ursinus from the Pribilof Islands, Alaska, using stable nitrogen (δ 15 N) and carbon (δ 13 C) isotope analyses of their fur, muscle, blubber, brain, liver, and kidney tissues. Mean δ 15 N values were non-uniform between tissues and ranged from 14.9‰ (fur) to 17.1‰ (lipid extracted blubber). Mean δ 13 C values also varied with tissue type and ranged from -24.7‰ (non-lipid extracted blubber) to -17.5‰ (fur). Mean isotope values of tissues clustered into groups coincident with their estimated protein and isotope turnover times, with fur representing the most remote incor

The population structure of grey seals Halichoerus grypus has previously been studied using molecular biological techniques. These works may be complemented by studies of certain ecological factors which play an important role in providing information on habitat usage, dietary behaviour, local migrations, distribution and social structure. One such factor is the fatty acid composition of depot fats, which is strongly influenced by the fatty acid composition found in the prey. To examine the extent to which the fatty acid composition of seal depot fats can be used to distinguish between populations, blubber biopsy samples were obtained from female grey seals at 2 Scottish breeding sites, Rona (n = 23) and the Isle of May (n = 34) and the fatty acid compositions determined by gas chromatography. The patterns obtained were compared using both univariate and multivariate statistical procedures. Fatty acid profiles at the 2 breeding sites could be clearly differentiated, with only 1 seal out of 57 being mis-classified. Thus, on the basis of blubber fatty acid composition, they may be regarded as 2 distinct foraging groups.

Organochlorine compounds (OC) are known to induce vitamin A (retinoids) deficiency in mammals, which may be associated with impairment of immunocompetence, reproduction and growth. This makes retinoids a potentially useful biomarker of organochlorine impact on marine mammals. However, use of retinoids as a biomarker requires knowledge about its intrapopulation patterns of variation in natural conditions, information which is not currently available. We investigated these patterns in a cetacean population living in an unpolluted environment. 100 harbour porpoises Phocoena phocoena from West Greenland were sampled during the 1995 hunting season. Sex, age, morphometrics, nutritive condition, and retinol (following saponification) and OC levels in blubber were determined for each individual. OC levels found were extremely low and therefore considered unlikely to affect the population adversely: mean blubber concentrations, expressed on an extractable basis, were 2.04 (SD = 1.1) ppm for PCBs and 2.76 (SD = 1.66) ppm for tDDT. The mean blubber retinol concentration for the overall population was 59.66 (SD = 45.26) mu g g(-1). Taking into account the high contribution of blubber to body mass, blubber constitutes a significant body site for retinoid deposition in harbour porpoises. Retinol concentrations did not differ significantly between geographical regions or sexes, but they did correlate significantly (p

This review presents a comparative analysis of the behaviour and energetics of the ice-breeding phocid seals of the North Atlantic in relation to their habitat(s). In very broad terms, it suggests that the term 'ice-breeding' is too simplistic and may lead to misconceptions about the actual degree of variability that exists in the breeding habitats of seals that do not give birth on land. The variation that exists within ice habitats is quite remarkable in terms of: temporal and structural stability of the pupping platform; the degree to which animals have access to the water; the risk of predation; and perhaps also the local availability of food. These factors all appear to influence the behaviour of mothers and pups and the allocation of energy during the lactation period of the species studied. Two basically different nursing strategies can be identified that may have evolved, at least in part, as a consequence of variation in these variables. The pattern displayed by grey (Halichoerus grypus), harp (Phoca groenlandica) and hooded (Cystophora cristata) seals involves a short lactation period, during which a large amount of energy is transferred from the mother to the pup through extremely-energy-rich milk. Pups of these species are very inactive and consequently a very high proportion of the received energy can be stored as body tissue, mainly in the form of subcutaneous blubber. The mothers generally feed little or not at all during the nursing period and the pups are weaned abruptly, having not yet entered the water in most cases, The other strategy, found in bearded (Erignathus barbatus) and ringed (Phoca hispida) seals, involves a longer lactation period, where less-energy-rich milk is transferred to very active pups. These pups learn to swim and dive during the nursing period, and are weaned with body compositions that are similar to those of adults. The mothers feed during lactation and weaning is less abrupt, with pups feeding independently, while still receiving milk from their mothers.

Fatty acid signature analysis was used to investigate the diet and the spatial scales of foraging in harbor seals Phoca vitulina richardsi in Prince William Sound (PWS) and elsewhere in the Gulf of Alaska. Blubber samples collected in 1994 and 1995 from 104 harbor seals from PWS, Kodiak Island, and southeast Alaska were analyzed for fatty acid composition. A total of 163 potential prey samples representing 10 taxa were collected and individually analyzed for total fat content and fatty acid composition. Approximately 70 fatty acids and isomers were found in both harbor seals and their prey. Classification and regression tree analysis was used to classify seals and prey according to their fatty acid signatures. Large differences were found in the fatty acid composition of blubber from seals sampled at Kodiak, southeast Alaska and PWS, over a broad geographical scale of 400 to 800 km. Additionally, fatty acid signatures distinguished seals from different regions within PWS, as well as on fine-scale resolutions of specific haulout sites within 9 to 15 km of one another. These findings suggest that seals forage site-specifically. These conclusions are supported by prey fatty acid patterns, which also differed on similarly small spatial scales within PWS. Not only could prey species such as herring Clupea pallasi and pollock Theragra chalcogramma be differentiated from one another using fatty acid signatures, but they could also be differentiated from one another using fatty acid signatures, but they could also be distinguished by size-class and location within PWS, reflecting differences in diet with age and as well as with fine-scale habitat. Results from this study are consistent with both satellite data from tagged harbor seals and stomach content analyses of forage fish species in PWS. Although preliminary, analyses suggest that large herring and pollock, as well as flatfish, may have dominated the diet of seals in southern PWS, whereas diets of seals in northern and eastern PWS may have been comprised more of small size classes of herring and pollock, and perhaps other items such as cephalopods, sandlance Ammodytes hexapterus, cod Gadus macrocephalus, and shrimp. We conclude that fatty acid signature analysis will be an important contribution to understanding marine food webs in estuarine and other marine environments.