Biochemical parameters of blood plasma of the harp seal Pagophilus groenlandicus Erxleben, 1777 (Pinnipedia, Procidae) of various ages

Results of study of several blood biochemical parameters of the harp seal Pagophilus groenlandicus Erxleben, 1777, from birth to the adult state are presented. The following age groups of the animals have been studied--newborns, 1.5-2 months, 1 year, 2 years, 3 years, and adults (older than 6 months). The content of total protein and its fractions, free amine nitrogen, urea, creatinine, glucose, total lipids, total calcium, and inorganic phosphorus was determined in the seal blood plasma. Differences of the degree of expression of levels of all studied parameters in the course of early postnatal ontogenesis of the animals have been established. The most significant metabolic changes in the harp seals were revealed at the period of end of weaning and transition to independent ingestion and then after the first year of life.     

Hematology and serum chemistry of harp (Phoca groenlandica) and hooded seals (Cystophora cristata) during the breeding season, in the Gulf of St. Lawrence, Canada

Standard hematologic and serum chemistry parameters were determined from 28 harp seals (Phoca groenlandica) and 20 hooded seals (Cystophora cristata) sampled from 6 March 2001 to 13 March 2001 during the breeding season. Whole blood was collected immediately postmortem from harp seal mother-pup pairs and from six hooded seal pups, and from live-captured adult hooded seals and three hooded seal pups; blood was analyzed within 24 hr at a local human hospital. A certified veterinary laboratory validated subsamples of whole blood and analyzed all serum chemistry parameters. Significant interlaboratory differences in mean values of packed cell volume (PCV) and mean cell volume (MCV) were found. Significant differences were found between samples from the five seal groups (adult male hooded seals, lactating female hooded seals, unweaned hooded seal pups; lactating female harp seals, and unweaned harp seal pups) for hematology and most serum chemistry parameters. In general, age-class influenced mean values of PCV, hemoglobin (HB), red blood cell (RBC) counts, MCV, mean cell hemoglobin (MCH), mean cell hemoglobin concentration (MCHC), and nucleated red blood cell (NRBC) counts per 100 leucocytes, but most age-related variations were species specific. Harp seal pups had significantly lower mean values of HB, PCV, MCH, and MCHC than did other seal groups, and significantly lower mean RBC counts than did hooded seal pups. Mean NRBC counts per 100 leukocytes were more than three times higher in harp seal pups than in hooded seal pups, but this difference was not statistically significant. Mean MCV were significantly lower in harp and hooded seal pups compared to those of adult harp and hooded seals. Differences in hemograms between pup species were likely because of the precocious development of hooded seal pups, which are weaned within 4 days, compared to 12 days for harp seal pups. Among adult seal groups, male hooded seals had significantly higher mean values of PCV and HB than did female harp and hooded seals, and significantly higher mean RBC counts than did adult female hooded seals. Among adult females, mean values of MCH and MCHC were statistically higher in hooded seals than in harp seals. Adult female harp and hooded seals did not differ significantly in other RBC parameters and mean leukocyte counts. Mean values of glucose, blood urea nitrogen, total bilirubin, alanine aminotransferase (ALT), alkaline phosphatase (ALP), total protein, and albumin showed species-specific variations between adults and pups. Except for ALP, few significant differences in mean enzyme activities of aspartate aminotransferase (AST), ALT, creatine kinase and gamma-glutamyltransferase were found between seal groups. Mean concentrations of electrolytes (calcium, phosphorus, sodium, potassium, chloride, magnesium, and total carbon dioxide) varied with age class, but variations in potassium and magnesium were species specific. Harp seal pups had significantly higher mean phosphorus and potassium levels compared to other seal groups.     

Modified albumin in harp seal blood serum

The content of modified albumin (Am) in harp seal (Pagophilus groenlandica Erxleben, 1777) blood serum was studied. Am was determined by paper electrophoresis by means of re-precipitation in the trichloroacetic acid-ethanol system. Modified albumin content in normal seal pups' blood serum increased from 1990 to 1994. The Am level in undernourished pups was stable from year to year and higher than in normal pups. In oceanarium investigations it was revealed a low albumin resistance to denaturation and the dependence of Am content on the animals' physiological state. Thus there is a possibility to regard modified albumin content as one of the significant parameters in biomonitoring of harp seal population and, moreover, as a supplementary criterion for estimation of seals' health state in captivity.     

Structure of the adrenal glands of Greenland seal Pagophilus groenlandica Erxleben, 1777 (Phocidae)

The harp seal adrenal gland studied is alike that of terrestrial mammals, but has some peculiarities. Firstly, this is presence of the fetal cortex in the adrenal gland without any signs of involution and degeneration in adult animals. This phenomenon has been previously described only for the horse adrenal gland. The glomerular zone of the cortex peculiar for the adrenals in the terrestrial mammals in the species studied has the form of arches. This property is also characteristic only to the horse gland. The absence of intermediate and juxtamedullary zones also differs the harp seal adrenal gland from that of terrestrial mammals.     

Mineral content of blood serum in greenland seal pups during the period of adaptation to the captivity

Results of investigation of mineral levels in the harp seal pups blood serum in connection with adaptation to the captivity are presented. The contents of copper, zinc, iron, magnesium, cobalt, manganese, sodium, potassium, calcium and phosphorus in the first 18 day of animals keeping in the oceanarium were determined. The causes of the revealed differences in changes of the contents of single elements during the observation term, and also question on duration of fading stress alterations and stabilization of biochemical parameters of marine mammals blood are discussed.     

Monoclonal antibody to alkaline phosphatase from the intestinal mucosa of the harp seal, Phoca groenlandica.

1. Hybridoma secreting a monoclonal antibody APP.1 to the harp seal alkaline phosphatase (A1Ph) was obtained by fusing murine myeloma Sp 2/0 cells with the splenocytes of BALB/c mice immunized with purified isozyme K. 2. The antibody has no effect on the enzyme activity and shows a high affinity for harp seal A1Ph (KD = 8.5 x 10(-10) M). The antibody has similar affinities for the AlPh of harp seal, fur seal, common seal and deer. 3. The antibody APP.1 was coupled to Sepharose and employed in chromatographic purification of the harp seal intestinal AlPh. Alkaline phosphatase isolated on this immunosorbent has a spec. act. of 20,800 units per mg of protein. 4. The antibody-enzyme complex gives an excellent immunocytochemical labeling of tissue sections, cell cultures and smears.     

The effects of climate change on harp seals (Pagophilus groenlandicus)

Harp seals (Pagophilus groenlandicus) have evolved life history strategies to exploit seasonal sea ice as a breeding platform. As such, individuals are prepared to deal with fluctuations in the quantity and quality of ice in their breeding areas. It remains unclear, however, how shifts in climate may affect seal populations. The present study assesses the effects of climate change on harp seals through three linked analyses. First, we tested the effects of short-term climate variability on young-of-the year harp seal mortality using a linear regression of sea ice cover in the Gulf of St. Lawrence against stranding rates of dead harp seals in the region during 1992 to 2010. A similar regression of stranding rates and North Atlantic Oscillation (NAO) index values was also conducted. These analyses revealed negative correlations between both ice cover and NAO conditions and seal mortality, indicating that lighter ice cover and lower NAO values result in higher mortality. A retrospective cross-correlation analysis of NAO conditions and sea ice cover from 1978 to 2011 revealed that NAO-related changes in sea ice may have contributed to the depletion of seals on the east coast of Canada during 1950 to 1972, and to their recovery during 1973 to 2000. This historical retrospective also reveals opposite links between neonatal mortality in harp seals in the Northeast Atlantic and NAO phase. Finally, an assessment of the long-term trends in sea ice cover in the breeding regions of harp seals across the entire North Atlantic during 1979 through 2011 using multiple linear regression models and mixed effects linear regression models revealed that sea ice cover in all harp seal breeding regions has been declining by as much as 6 percent per decade over the time series of available satellite data.     

Changing subsistence practices at the Dorset Paleoeskimo site of Phillip's Garden, Newfoundland

A comparison of identified faunal assemblages from the Dorset site of Phillip's Garden indicates that harp seal hunting was the main focus of activity throughout the site's occupation. Despite the highly specialized nature of site use, it appears that reliance on harp seal decreased over time while fish and birds became increasingly important. These changes may reflect longer seasonal occupations at the site in later centuries, and/or a decrease in the local availability of harp seal. The observed shift coincides with the onset of a local climatic warming trend, which might have affected harp seal movements in the area. Dorset subsistence and settlement patterns in Newfoundland are still poorly understood due to a lack of preserved faunal assemblages in the region. The temporal trend illustrated here indicates that we cannot assume that these patterns were static throughout the Dorset occupation of the island.     

Health status of harp seals (Phoca groenlandica) and hooded seals (Cystophora cristata) on Sable Island,Nova Scotia,Canada, concurrent with their expanding range

Beach surveys for harp (Phoca groenlaandica) and hooded (Cystophora cristata) seals documented a dramatic increase in their numbers on Sable Island in mid 1990s. In the 1980s, no more than five animals of both species were observed on this island each year, however, during late 1994 to 1998, 1,191 harp and 870 hooded seals, mostly young animals, were recorded. Although some of these seals had been killed by sharks, most (roughly 75%) were found alive or as intact carcasses on the beach, and some of the live seals were later found dead. Emaciation/starvation was considered the primary cause of death in seals that were not obviously killed by sharks. Factors that may have compounded this poor body condition included gastric impaction with abnormal ingesta, hemorrhagic diathesis possibly induced by parasitic migration and secondary vasculitis, and stomatitis (in hooded seals only). Some harp and hooded seals expanding their range in recent years may be unable to feed successfully, although the reasons for this are unclear.     

Size and distribution of oxygen stores in harp and hooded seals from birth to maturity

Pinnipeds rely primarily on oxygen stores in blood and muscles to support aerobic diving; therefore rapid development of body oxygen stores (TBO₂) is crucial for pups to transition from nursing to independent foraging. Here, we investigate TBO₂ development in 45 harp (Pagophilus groenlandicus) and 46 hooded (Cystophora cristata) seals ranging in age from neonates to adult females. We found that hooded seal adults have the largest TBO₂ stores yet reported (89.5 ml kg⁻¹), while harp seal adults have values more similar to other phocids (71.6 ml kg⁻¹). In adults, large TBO₂ stores resulted from large blood volume (harp169, hood 194 ml kg⁻¹) and high muscle Mb content (harp 86.0, hood 94.8 mg g⁻¹). In contrast, pups of both species had significantly lower mass-specific TBO₂ stores than adults, and stores declined rather than increased during the nursing period. This decline was due to a reduction in mass-specific blood volume and the absence of an increase in the low Mb levels (harp 21.0, hood 31.5 mg g⁻¹). Comparisons with other phocid species suggests that the pattern of blood and muscle development in the pre- and post-natal periods varies with terrestrial period, and that muscle maturation rates may influence the length of the postweaning fast. However, final maturation of TBO₂ stores does not take place until after foraging begins.     

Summer feeding ecology of harp seals (Phoca groenlandica) in relation to arctic cod (Boreogadus saida) in the Canadian high arctic

Summary The diet and feeding behaviour of harp seals, Phoca groenlandica, was examined in two high arctic locations. Fish otoliths were used to evaluate dietary composition and aspects of the population dynamics of the major prey species, arctic cod, Boreogadus saida. Harp seals, primarily adults, arrive in the high arctic in mid to late June and depart by early October. Their migration is undertaken specifically for feeding. Harp seals feed intensively on arctic cod, often occurring in dense multispecies aggregations in late summer. The average weight of harp seal stomach contents was high; glutted individuals contained as much as 6% of their body weight in food. Although arctic cod declined in abundance between years, size of cod ingested was similar between areas and years, and overlapped completely with cod taken by other marine mammals. Age/size segregation of arctic cod may account for poor representation of fish <3 years old in the seal diet. Widespread reproductive failure of arctic cod could have a profound influence on the energy balance of adult harp seals since there does not appear to be an alternate food source of equivalent energy value and abundance in arctic waters. Increasing harp seal populations will likely result in increased competition with a host of arctic cod predators, particularly ringed seals.     

DIET OF WEANED PUPS AND SEASONAL VARIATIONS IN BODY CONDITION OF JUVENILE BARENTS SEA HARP SEALS PHOCA GROENLANDICA

Data on blubber depth, body condition, and diet were collected from young of year and juvenile harp seals ( Phoca groenlandica ) in the Barents Sea in the periods February-April and June-October 1990–1997. Harp seal pups feed independently shortly after weaning. In the southern parts of the Barents Sea the diet of harp seal pups consisted mainly of euphausiids ("krill") Thysanoessa sp. and amphipods of the genus Parathemisto . The change in body condition of harp seal pups between weaning (mid-March) and June indicated that considerable amounts of blubber energy, deposited during suckling, were mobilized. This suggests that the early food intake of weaned pups was insufficient to meet the energy requirements. The pattern of low spring and earlysummer body condition, followed by a subsequent rapid improvement in condition during late summer and autumn appeared to occur not only among pups-of-the-year, but also in one- and two-year old harp seals.     

The harp seal, Pagophilus groenlandicus (Erxleben, 1777). XVII. Structure and metabolic adaption of the caval sphincter muscle with some observations on the diaphragm.

Three types of fibre, dark (type 1), light (type 2) and intermediate, were distinguished in the caval sphincter muscle of the diaphragm in the harp seal (Pagophilus groenlandicus) using histochemical and electron-microscopic techniques. The dark fibre contained large peripheral aggregations of mitochondria, numerous lipid droplets and dense aggregates of glycogen granules. The same features were observed in the dark fibre of the diaphragm muscle too. In the light of the low oxidative enzyme activity and high lipase activity observed in the diaphragm and other skeletal muscles of the harp seal in previous studies, it is postulated that these mitochondrial aggregations and lipid droplets represent an adaptation for the generation of heat through non-shivering thermogenesis comparable to that in the brown adipose tissue. Such ability to generate and maintain heat by uncoupling the oxidative phosphorylation process should enable the caval sphincter muscle to function efficiently in regulating the cardiac return of blood from the inferior vena cava during a dive when the body temperature as a whole drops. The lack of the regional differences in the fibre composition of the harp seal diaphragm, as were reported in the rat diaphragm, is attributed to the seal's large body size, lower metabolic rate and diving habit.     

Factors Affecting Harp Seal (Pagophilus groenlandicus) Strandings in the Northwest Atlantic

The effects of climate change on high latitude regions are becoming increasingly evident, particularly in the rapid decline of sea ice cover in the Arctic. Many high latitude species dependent on sea ice are being forced to adapt to changing habitats. Harp seals (Pagophilus groenlandicus) are an indicator species for changing high-latitude ecosystems. This study analyzed multiple factors including ice cover, demographics, and genetic diversity, which could affect harp seal stranding rates along the eastern coast of the United States. Ice cover assessments were conducted for the month of February in the Gulf of St. Lawrence whelping region from 1991–2010 using remote sensing data, and harp seal stranding data were collected over the same time period. Genetic diversity, which may affect how quickly species can adapt to changing climates, was assessed using ten microsatellite markers to determine mean d ² in a subset of stranded and by-caught (presumably healthy) seals sampled along the northeast U.S. coast. Our study found a strong negative correlation (R ² = 0.49) between ice cover in the Gulf of St. Lawrence and yearling harp seal strandings, but found no relationship between sea ice conditions and adult strandings. Our analysis revealed that male seals stranded more frequently than females during the study period and that this relationship was strongest during light ice years. In contrast, we found no significant difference in mean d ² between stranded and by-caught harp seals. The results demonstrate that sea ice cover and demographic factors have a greater influence on harp seal stranding rates than genetic diversity, with only a little of the variance in mean d ² among stranded seals explained by ice cover. Any changes in these factors could have major implications for harp seals, and these findings should be considered in the development of future management plans for the Arctic that incorporate climate variability.     

THERMAL FUNCTION OF PHOCID SEAL FUR

In phocid seals, blubber serves as the main thermal insulation instead of fur. The thermal function of fur, at least in adult phocid seals, has therefore been questioned. We measured the relative contribution of fur to the combined thermal resistance (insulation) offered by blubber, skin, and fur in newborn and adult harp ( Pagophilus groenlandicus ) and hooded ( Cystophora cristata ) seals, in air and water, to elucidate the role of fur as insulation in phocid seals. In air the fur contributed 90% of the combined thermal resistance of blubber, skin, and fur in newborn harp seal pups and 29% in adulrs, whereas in hooded seals the fur contributed 73% in newborn pups and 34% in adults. When submerged the thermal resistance of the fur was reduced by 84%-92%, and contributed 65% to the total insulation in newborn harp seal pups and 3% in adults, and 26% in newborn hooded seal pups and 5% in adults. We conclude that in air the fur of phocid seals makes an important contribution to the insulation of pups, and also contributes considerably to the insulation of adult animals. In water, even though the thermal resistance of the fur is dramatically reduced, the fur still contributes substantially to the insulation of pups, but its contribution in adults is negligible.     

Multi-decadal trends in biomarkers in harp seal teeth from the North Atlantic reveal the influence of prey availability on seal trophic position

Arctic food webs are being impacted by borealisation and environmental change. To quantify the impact of these multiple forcings, it is crucial to accurately determine the temporal change in key ecosystem metrics, such as trophic position of top predators. Here, we measured stable nitrogen isotopes (δ¹⁵N) in amino acids in harp seal teeth from across the North Atlantic spanning a period of 60 years to robustly assess multi-decadal trends in harp seal trophic position, accounting for changes in δ¹⁵N at the base of the food web. We reveal long-term variations in trophic position of harp seals which are likely to reflect fluctuations in prey availability, specifically fish- or invertebrate-dominated diets. We show that the temporal trends in harp seal trophic position differ between the Northwest Atlantic, Greenland Sea and Barents Sea, suggesting divergent changes in each local ecosystem. Our results provide invaluable data for population dynamic and ecotoxicology studies.     

Large increases of harp seals (Phoca groenlandica) and hooded seals (Cystophora cristata) on Sable Island, Nova Scotia, since 1995

Beach surveys for harp (Phoca groenlandica) and hooded (Cystophora cristata) seals documented a dramatic increase in their numbers on Sable Island in the mid-1990s. From late 1994 to 1998, 1,191 harp and 870 hooded seals, mostly young animals, were recorded on the island whereas, in the 1980s, no more than 5 animals of both species were observed each year. Of the 2,061 harp and hooded seals examined, 41.7% were found alive, 26.7% were killed by sharks, and 31.6% were found dead but intact. This increase in numbers of harp and hooded seals on Sable Island, which is south of their historic northern range, is consistent with the recent increase of extralimital occurrences of these species along the east coast of North America. However, the large number of seals recorded in this study provides more information on their demography than has previously been possible.     

DIGESTIBILITY OF CRUSTACEANS and CAPELIN IN HARP SEALS (PHOCA GROENLANDICA)

Gross energy intake (GEI), apparent digestible efficiency (%DE), and body-mass change were studied both in recently weaned and in subadult harp seals fed capelin ( Mallotus villosus ) and crustaceans ( Parathemisto libellula and Thysanoessa sp.) ad lib. The median %DE of Parathemisto libellula (with a wet-weight energy density (ED) of 3.9 kJ/g) and Thysanoessa sp. (ED: 2.3 kJ/g) was 81% and 83%, respectively, while the median %DE of capelin (ED: 8.6 kJ/g) was 94% and 93% for subadult harp seals and one harp seal pup, respectively. No correlation between age and %DE was obtained (P > 0.05). Despite ad lib. access to the food, the harp seal pups were unable to maintain body mass while on a crustacean diet, and it is therefore suggested that harp seal pups most likely must supplement their crustacean diets with fish to maintain growth.     

ESTIMATING STRUCK AND LOSS RATES FOR HARP SEALS (PAGOPHILUS GROENLANDICUS) IN THE NORTHWEST ATLANTIC

One of the major sources of unreported mortality during the commercial harp seal ( Pagophilus groenlandicus ) hunt in the Northwest Atlantic is the number of animals that are killed but not recovered or reported, commonly referred to as struck and lost. With the significant expansion of the hunt in Canada and in Greenland during the mid-1990s, there is a concern that the number of seals lost may have reached a level that is not sustainable relative to current harvest levels. To address this problem a study examining struck and loss rates was initiated in 1998 and 1999. Loss rates for young seals taken on the ice varied from 0% to 1.9% and from 0% to 10.0% when taken in the water. Seals greater than one year of age had loss rates of 0%–4.9% when taken on the ice and 13.8%-50.0% when taken in the water. These estimates are lower than those recently reported for Northwest Atlantic harp seals.