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The circumpolar Arctic ringed seal (Pusa hispida) occupies its fast-ice breeding habitat for four to five months during winter and the pack ice or open water of adjacent areas for the rest of the year. From 1971 – 78 and 1992 – 2019, we sampled approximately 100 ringed seals annually from western Prince Albert Sound (WPAS), the prime ringed seal fast-ice breeding habitat in Canada’s Western Arctic, adjacent to primary overwinter foraging habitat in eastern Amundsen Gulf (EAG). As our metric of body condition, we measured ventral blubber depth corrected for body size. As our metrics of reproduction, we measured the annual ovulation rate of multiparous females and percent pups in the open-water harvest. We examined these biological parameters in relation to the winter Arctic Oscillation Index (winAOI) and the timing of sea ice clearance in EAG in spring. There were no significant effects of age or sample month (June or July) on adult blubber depth, but significant sex and year effects and, in females, ovulation status effects. Across the series, as we have observed previously through 2011, there was a sustained temporal declining trend in blubber depth in adults of both sexes. There was no temporal trend in residual blubber depth, no correlation between blubber depth and sea ice clearance date in EAG, and a quasi-cyclic pattern in blubber depth that tracked some of the phases of the winAOI. Annual ovulation rates were mainly in the 80% – 100% range and correlated with percent pups in the open harvest in the same year. Three (1974, 2005, 2012) of the 36 y experienced reproductive failures, when over 50% of the multiparous females failed to ovulate. In each case, ovulation rates returned to normal within 1 – 3 y. Low annual ovulation rates were correlated with late sea ice clearance in EAG in spring, with two widespread ovulation failure events taking place in years when spring sea ice clearance was delayed by five to six weeks. The most recent ovulation failure (2012) differed in that it came in an average ice year but at the end of a six-year sequence of negative residual mean blubber depths. Earlier spring sea ice clearance in WPAS, based on the observed rate of 3.8 d per decade, would on average not result in the physical loss of sea ice for pupping in this core habitat before 2140. The mechanisms involved in the sustained declining temporal trend in body condition, linkage with some phases of the winAOI, and the temporary but episodic failures of ovulation are complex and not fully explained by either the timing of sea ice clearance or the winAOI. Until the complex mix of factors, pressures and responses are understood, our ability to predict the impacts of a changing climate on ringed seals will remain limited.

The ringed seal is a small phocid seal that has a northern circumpolar distribu-tion. It has long been recognized that body size is variable in ringed seals, and it has been suggested that ecotypes that differ in size exist. This study explores patterns of body size (length and girth) and age-at-maturity across most of the Arctic subspecies’ range using morphometric data from 35 sites. Asymptotic lengths varied from 113 to 151 cm, with sites falling into five distinct size clus-ters (for each sex). Age-at-maturity ranged from 3.1 to 7.4 years, with sites that had early ages of sexual maturity generally having small length-at-maturity and small final body length. The sexes differed in length at some sites, but not in a consistent pattern of dimorphism. The largest ringed seals occurred in western Greenland and eastern Canada, and the smallest occurred in Alaska and the White Sea. Latitudinal trends occurred only within sites in the eastern Canadian Arctic. Girth (with length and season accounted for) was also highly variable but showed no notable spatial pattern; males tended to be more rotund than females. Genetic studies are needed, starting with the “giants” at Kangia (Greenland) and in northern Canada to determine whether they are genetically distinct ecotypes. Additional research is also needed to understand the ecological linkages that drive the significant regional size differences in ringed seals that were confirmed in this study, and also to understand their implications with respect to potential adaptation to climate change.

Harp seals (Pagophilus groenlandicus) that breed in February and March in the White Sea migrate to open water around Svalbard and Franz Josef Land in the Barents Sea, feeding pelagically while following the receding ice edge northward to the edge of the polar pack. Although harp seals are present throughout the area during the summer, they are primarily pelagic and do not appear to be extensively preyed upon by polar bears (Ursus maritimus). However, occasionally, large numbers of harp seals may haul out and rest on the pack ice or feed in the water below the ice and surface to breathe between the floes. When approached by a polar bear while on the ice, harp seals do not exhibit the instant flight response characteristic of the polar bear’s primary prey species, ringed (Pusa hispida) and bearded seals (Erignathus barbatus). In this situation, polar bears may make multiple kills without either consuming their own prey or scavenging seals killed by other bears. This behavior appears not to frighten other nearby harp seals, whether hauled out on the ice or in the water below the floes. These unusual concentrations of harp seals hauled out on sea ice may be related to the distribution and abundance of fish or other epontic prey. Their lack of an escape response to predators on the surface of the sea ice is probably a result of briefly hauling out in large numbers in spring while whelping on the sea ice in areas where the consequences of potential polar bear predation are insignificant. The rare events of harp seal mortality from bears killing them on the surface of pack ice during the summer do not appear to have a significant impact at the population level of either species.

Evolutionary explanations for mammalian sociality typically center on inclusive-fitness benefits of associating and cooperating with close kin, or close maternal kin as in some whale societies, including killer and sperm whales. Their matrilineal structure has strongly influenced the thinking about social structure in less well-studied cetaceans, including beluga whales. In a cross-sectional study of group structure and kinship we found that belugas formed a limited number of distinct group types, consistently observed across populations and habitats. Certain behaviours were associated with group type, but group membership was often dynamic. MtDNA-microsatellite profiling combined with relatedness and network analysis revealed, contrary to predictions, that most social groupings were not predominantly organized around close maternal relatives. They comprised both kin and non-kin, many group members were paternal rather than maternal relatives, and unrelated adult males often traveled together. The evolutionary mechanisms that shape beluga societies are likely complex; fitness benefits may be achieved through reciprocity, mutualism and kin selection. At the largest scales these societies are communities comprising all ages and both sexes where multiple social learning pathways involving kin and non-kin can foster the emergence of cultures. We explore the implications of these findings for species management and the evolution of menopause.

Pulmonary ventilation and pulmonary arterial pressure both rise progressively during the first few hours of human acclimatization to hypoxia. These responses are highly variable between individuals, but the origin of this variability is unknown. Here, we sought to determine whether the variabilities between different measures of response to sustained hypoxia were related, which would suggest a common source of variability. Eighty volunteers individually underwent an 8-h isocapnic exposure to hypoxia (end-tidal P(O2)=55 Torr) in a purpose-built chamber. Measurements of ventilation and pulmonary artery systolic pressure (PASP) assessed by Doppler echocardiography were made during the exposure. Before and after the exposure, measurements were made of the ventilatory sensitivities to acute isocapnic hypoxia (G(pO2)) and hyperoxic hypercapnia, the latter divided into peripheral (G(pCO2)) and central (G(cCO2)) components. Substantial acclimatization was observed in both ventilation and PASP, the latter being 40% greater in women than men. No correlation was found between the magnitudes of pulmonary ventilatory and pulmonary vascular responses. For G(pO2), G(pCO2) and G(cC O2), but not the sensitivity of PASP to acute hypoxia, the magnitude of the increase during acclimatization was proportional to the pre-acclimatization value. Additionally, the change in G(pO2) during acclimatization to hypoxia correlated well with most other measures of ventilatory acclimatization. Of the initial measurements prior to sustained hypoxia, only G(pCO2) predicted the subsequent rise in ventilation and change in G(pO2) during acclimatization. We conclude that the magnitudes of the ventilatory and pulmonary vascular responses to sustained hypoxia are predominantly determined by different factors and that the initial G(pCO2) is a modest predictor of ventilatory acclimatization.

Background The von Hippel–Lindau tumour suppressor protein–hypoxia-inducible factor (VHL–HIF) pathway has attracted widespread medical interest as a transcriptional system controlling cellular responses to hypoxia, yet insights into its role in systemic human physiology remain limited. Chuvash polycythaemia has recently been defined as a new form of VHL-associated disease, distinct from the classical VHL-associated inherited cancer syndrome, in which germline homozygosity for a hypomorphic VHL allele causes a generalised abnormality in VHL–HIF signalling. Affected individuals thus provide a unique opportunity to explore the integrative physiology of this signalling pathway. This study investigated patients with Chuvash polycythaemia in order to analyse the role of the VHL–HIF pathway in systemic human cardiopulmonary physiology. Methods and Findings Twelve participants, three with Chuvash polycythaemia and nine controls, were studied at baseline and during hypoxia. Participants breathed through a mouthpiece, and pulmonary ventilation was measured while pulmonary vascular tone was assessed echocardiographically. Individuals with Chuvash polycythaemia were found to have striking abnormalities in respiratory and pulmonary vascular regulation. Basal ventilation and pulmonary vascular tone were elevated, and ventilatory, pulmonary vasoconstrictive, and heart rate responses to acute hypoxia were greatly increased. Conclusions The features observed in this small group of patients with Chuvash polycythaemia are highly characteristic of those associated with acclimatisation to the hypoxia of high altitude. More generally, the phenotype associated with Chuvash polycythaemia demonstrates that VHL plays a major role in the underlying calibration and homeostasis of the respiratory and cardiovascular systems, most likely through its central role in the regulation of HIF., Editors' Summary Background. Human cells (like those of other multicellular animals) use oxygen to provide the energy needed for daily life. Having not enough oxygen is a problem, but having too much is also dangerous because it damages proteins, DNA, and other large molecules that keep cells functioning. Consequently, the physiological systems—including the heart, lungs, and circulation—work together to balance oxygen supply and demand throughout the body. When oxygen is limiting (a condition called hypoxia), as happens at high altitudes, the cellular oxygen supply is maintained by increasing the heart rate, increasing the speed and depth of breathing (hyperventilation), constricting the blood vessels in the lung (pulmonary vasoconstriction), and increasing the number of oxygen-carrying cells in the blood. All these physiological changes increase the amount of oxygen that can be absorbed from the air, but how they are regulated is poorly understood. By contrast, researchers know quite a bit about how individual cells respond to hypoxia. When oxygen is limited, a protein called hypoxia-inducible factor (or HIF) activates a number of target proteins that help the cell get enough oxygen (for example, proteins that stimulate the growth of new blood vessels). When there is plenty of oxygen, another protein, called von Hippel–Lindau tumor suppressor (abbreviated VHL), rapidly destroys HIF. Recently, researchers discovered that a genetic condition called Chuvash polycythaemia, characterised by the overproduction of red blood cells, is caused by a specific defect in VHL that reduces its ability to destroy HIF. As a result, the expression of certain HIF target proteins is increased even when oxygen levels are normal. Why Was This Study Done? Chuvash polycythaemia is very rare, and so far little is known about how this genetic abnormality affects the physiology and long-term health of patients. By studying heart and lung function in patients with Chuvash polycythaemia, the researchers involved in this study hoped to discover more about the health consequences of the condition and to find out whether the VHL–HIF system controls systemic responses to hypoxia as well as cellular responses. What Did the Researchers Do and Find? The researchers recruited and studied three patients with Chuvash polycythaemia, and, as controls for the comparison, several normal individuals and patients with an unrelated form of polycythaemia. They then measured how the lungs and hearts of these people reacted to mild hypoxia (similar to that experienced on commercial air flights) and moderate hypoxia (equiv alent to being on the top of an Alpine peak). They found that patients with Chuvash polycythaemia naturally breathe slightly quicker and deeper than normal individuals, and that their breathing rate increased dramatically and abnormally when oxygen was reduced. They also found that at normal oxygen levels the pulmonary blood vessels of these patients were more constricted than those of control individuals, and that they reacted more extremely to hypoxia. Similarly, the normal heart rate of the patients was slightly higher than that of the controls and increased much more in response to mild hypoxia. What Do These Findings Mean? The physiological differences measured by the researchers between Chuvash polycythaemia patients and control individuals are similar to the adaptations seen in people traveling to high altitudes where oxygen is limited. Thus, the VHL–HIF proteins may regulate the response to different oxygen concentrations both in individual cells and at the systemic level, although more physiological studies are needed to confirm this. Because the pulmonary blood vessels of patients with Chuvash polycythaemia are always abnormally constricted, and even more so when oxygen is limited, these people should avoid living at high altitude and should minimise air travel, suggest the researchers. The increased blood pressure in their lungs (pulmonary hypertension) could conceivably cause heart failure under such circumstances. Finally, this study has implications for the development of drugs directed at the VHL–HIF system. Agents are currently being designed to promote the development of new blood vessels after strokes or heart attacks by preventing the destruction of HIF, but based on the findings here such agents might have undesirable physiological affects. Conversely, HIF inhibitors (which act as anti-cancer reagents by increasing hypoxia in the centre of tumors and so inhibiting their growth) might be useful in the treatment of pulmonary hypertension. Additional Information. Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0030290. • Online Mendelian Inheritance in Man page on Chuvash polycythaemia • Information from the VHL Family Alliance on von Hippel–Lindau disease, including information on Chuvash polycythaemia • Wikipedia page on polycythaemia and von Hippel–Lindau disease (note: Wikipedia is a free online encyclopaedia that anyone can edit), Physiological study of patients with Chuvash polycythemia (caused by mutation of VHL) reveals characteristics similar to those associated with acclimatization to the hypoxia of high altitude.

The hypoxia-inducible factor (HIF) family of transcription factors is responsible for coordinating the cellular response to low oxygen levels in animals. By regulating the expression of a large array of target genes during hypoxia, these proteins also direct adaptive changes in the hematopoietic, cardiovascular, and respiratory systems. They also play roles in pathological processes, including tumorogenesis. In recent years, several oxygenases have been identified as key molecular oxygen sensors within the HIF system. The HIF hydroxylases regulate the stability and transcriptional activity of the HIF-alpha subunit by catalyzing hydroxylation of specific proline and asparaginyl residues, respectively. They require oxygen and 2-oxoglutarate (2OG) as co-substrates, and depend upon non-heme ferrous iron (Fe(II)) as a cofactor. This article summarizes current understanding of the biochemistry of the HIF hydroxylases, identifies targets for their pharmacological manipulation, and discusses their potential in the therapeutic manipulation of the HIF system.

The hypoxia-inducible factors (HIFs; isoforms HIF-1α, HIF-2α, HIF-3α) mediate many responses to hypoxia. Their regulation is principally by oxygen-dependent degradation, which is initiated by hydroxylation of specific proline residues followed by binding of von Hippel-Lindau (VHL) protein. Chuvash polycythemia is a disorder with elevated HIF. It arises through germline homozygosity for hypomorphic VHL alleles and has a phenotype of hematological, cardiopulmonary, and metabolic abnormalities. This study explores the phenotype of two other HIF pathway diseases: classic VHL disease and HIF-2α gain-of-function mutation. No cardiopulmonary abnormalities were detected in classic VHL disease. HIF-2α gain-of-function mutations were associated with pulmonary hypertension, increased cardiac output, increased heart rate, and increased pulmonary ventilation relative to metabolism. Comparison of the HIF-2α gain-of-function responses with data from studies of Chuvash polycythemia suggested that other aspects of the Chuvash phenotype were diminished or absent. In classic VHL disease, patients are germline heterozygous for mutations in VHL, and the present results suggest that a single wild-type allele for VHL is sufficient to maintain normal cardiopulmonary function. The HIF-2α gain-of-function phenotype may be more limited than the Chuvash phenotype either because HIF-1α is not elevated in the former condition, or because other HIF-independent functions of VHL are perturbed in Chuvash polycythemia.—Formenti, F., Beer, P. A., Croft, Q. P. P., Dorrington, K. L., Gale, D. P., Lappin, T. R. J., Lucas, G. S., Maher, E. R., Maxwell, P. H., McMullin, M. F., O'Connor, D. F., Percy, M. J., Pugh, C. W., Ratcliffe, P. J., Smith, T. G., Talbot, N. P., Robbins, P. A. Cardiopulmonary function in two human disorders of the hypoxia-inducible factor (HIF) pathway: von Hippel-Lindau disease and HIF-2α gain-of-function mutation.

When humans are exposed to hypoxia, systemic and intracellular changes operate together to minimise hypoxic injury and restore adequate oxygenation. Emerging evidence indicates that the hypoxia-inducible factor (HIF) family of transcription factors plays a central regulatory role in these homeostatic changes at both the systemic and cellular levels. HIF was discovered through its action as the transcriptional activator of erythropoietin, and has subsequently been found to control intracellular hypoxic responses throughout the body. HIF is primarily regulated by specific prolyl hydroxylase-domain enzymes (PHDs) that initiate its degradation via the von Hippel-Lindau tumour suppressor protein (VHL). The oxygen and iron dependency of PHD activity accounts for regulation of the pathway by both cellular oxygen and iron status. Recent studies conducted in patients with rare genetic diseases have begun to uncover the wider importance of the PHD-VHL-HIF axis in systems-level human biology. These studies indicate that, in addition to regulating erythropoiesis, the system plays an important role in cardiopulmonary regulation. This article reviews our current understanding of the importance of HIF in human systems-level physiology, and is modelled around the classic physiological response to high-altitude hypoxia.

In 1979, Smith et al. (1981) observed a group of seven killer whales (Orcinus orca) conduct a coordinated attack on a crabeater seal (Lobodon carcinophaga) by creating a wave to wash the hauled-out seal off floating ice. Since then a number of similar events have been witnessed along the Antarctic Peninsula. The increased tourist ship traffic in this area has provided an opportunity for many observers equipped with cameras and video recorders to document a number of these. Given that it is often difficult to gain an accurate description of events involving a number of killer whales moving quickly and typically under water, in an ice-filled environment, the availability of good quality video recordings is often the best way of documenting such a fast-moving incident. The vantage point is of importance and those observations from the bow of a large ship, which can maneuver to within a short distance of the animals, are of significantly better quality than those at water level. Still photography, in addition to video, is of particular importance in any attempt to identify individual whales or groups.

The activity within the autonomic nervous system may be altered following sustained exposure to hypoxia, and it is possible that this increase in activity underlies the early acclimatization of both ventilation and the pulmonary vasculature to hypoxia. To test this hypothesis, seven individuals were infused with the ganglionic blocker trimetaphan before and after an 8 h exposure to hypoxia. The short half-life of trimetaphan should ensure that the initial infusion does not affect acclimatization to the 8 h hypoxia exposure, and the use of a ganglion blocking agent should inhibit activity within all branches of the autonomic nervous system. During the infusions of trimetaphan, measurements of ventilation and echocardiographic assessments of pulmonary vascular tone (ΔPmax) were made during euoxia and during a short period of isocapnic hypoxia. Subjects were also studied on two control days, when a saline infusion was substituted for trimetaphan. Trimetaphan had no effect on either euoxic ventilation or the sensitivity of ventilation to acute hypoxia. Trimetaphan significantly reduced ΔPmax in euoxia (P < 0.05), but had no significant effect on the sensitivity of ΔPmax to acute hypoxia once changes in cardiac output had been controlled for. The 8 h period of hypoxia elevated euoxic ventilation (P < 0.001) and ΔPmax (P < 0.001) and increased their sensitivities to acute hypoxia (P < 0.001 for both), indicating that significant acclimatization had occurred. Trimetaphan had no effect on the acclimatization response of any of these variables. We conclude that altered autonomic activity following 8 h of hypoxia does not underlie the acclimatization observed in ventilation or pulmonary vascular tone.

We investigated whether ringed seal (Phoca hispida) use of breathing holes and lairs (structures) during winter and spring was affected by construction and drilling on Northstar Island, built in the nearshore Alaskan Beaufort Sea. Trained dogs searched the sea ice for structures within 3.5 km of Northstar during each of three survey periods: November/December 2000, March 2001, and May 2001. Temperature sensors were placed in 54 different ringed seal structures to determine dates of abandonment. Ringed seals created and used sea ice structures within 11 to 3,500 m of Northstar activities. Of the 35 structures located in November and December 2000, 68% had been abandoned by late May 2001. Of the 60 structures located in March 2001, 42% had been abandoned by late May 2001. During all surveys combined, 181 structures were located, and 118 (65%) were actively used by late May 2001. We used Cox regression to determine three primary factors influencing the abandonment of these structures: (1) structures found during later searches were significantly less likely to be abandoned; (2) structures in areas of higher ice deformation were significantly more likely to be abandoned; and (3) structures farther from the ice road to Northstar were more likely to be abandoned, though marginally significant. We would have predicted structures closer to Northstar would have been abandoned at higher rates if Northstar activities negatively affected seal use of structures. Ringed seals in the Alaskan Beaufort Sea appear to create and abandon structures throughout the winter and spring at rates higher than previously documented.

Hepcidin inhibits iron uptake from the gut and release of iron from macrophages in the reticuloendothelial system. Suppression of plasma hepcidin occurs in lowlanders after ascent to high altitude, reflecting the increased iron demand for erythropoiesis, but the mechanism and primary stimulus for hepcidin suppression in this setting remains unclear...

Oxygen-dependent regulation of the erythropoietin gene is mediated by the hypoxia-inducible factor (HIF) family of transcription factors. When oxygen is plentiful, HIF undergoes hydroxylation by a family of oxygen-dependent prolyl hydroxylase domain (PHD) proteins, promoting its association with the von Hippel-Lindau (VHL) ubiquitin E3 ligase and subsequent proteosomal degradation. When oxygen is scarce, the PHD enzymes are inactivated, leading to HIF accumulation and upregulation not only of erythropoietin expression, but also the expression of hundreds of other genes, including those coordinating cardiovascular and ventilatory adaptation to hypoxia. Nevertheless, despite the identification of over 50 mutations in the PHD-HIF-VHL pathway in patients with previously unexplained congenital erythrocytosis, there are very few reports of associated cardiopulmonary abnormalities. We now report exaggerated pulmonary vascular and ventilatory responses to acute hypoxia in a 35-year-old man with erythrocytosis secondary to heterozygous mutation in PHD2, the most abundant of the PHD isoforms. We compare this phenotype with that reported in patients with the archetypal disorder of cellular oxygen sensing, Chuvash polycythemia, and discuss the possible clinical implications of our findings, particularly in the light of the emerging role for small molecule PHD inhibitors in clinical practice.

In late May 1998, a large area of the land-fast ice in Prince Albert Sound, Northwest Territories bordering the Amundsen Gulf, broke up almost 1 month earlier than usual. In June and July, 92 neonate ringed seals were sampled. Of 50 examined in June 1998, 25 still had remains of their white lanugal pelage. In July, 2 of 42 pups collected still retained some of their white lanugal fur. The pups, with lanugo still showing, were in significantly poorer body condition than their fully moulted cohort members. Mean condition of moulted pups, in June 1998, was higher than that of moulted pups collected in June of 1971, 1972, 1976–1978, and 1993–1997. All indications were that marine productivity was high in June 1998. Fully moulted pups fed more on Arctic cod (Boreogadus saida) than did the smaller pups retaining some lanugal fur. Adult and juvenile seals fed primarily on Arctic cod. Mean lengths of lanugal pups and fully moulted pups in June were lower than predicted using growth equations. This may have resulted from later birth dates or shortened lactation and consequent slower growth, but the causes are not defined.

Lightweight untethered pneumatic darts were used to biopsy killer whales, Orcinus orca, for genetic and toxicological analysis. Samples of epidermal, dermal, and hypodermal tissue weighing approximately 0.5 g were obtained by 65% of the 91 darts fired during the study. Sufficient DNA for multiple analyses was extracted from the biopsies, which were also used for fatty acid and toxic contaminant analyses. Reactions such as momentary shakes or accelerations were observed after 81% of the dart hits and 53% of the misses. Aversion to the research vessel was assessed by reapproaching target whales after the sampling attempts. In 6% of the hits and 8% of the misses aversion to the research boat increased immediately following the attempt. No similar increases in aversion were seen when killer whales were reapproached one day to one year after being hit. The darts were also tested successfully on humpback whales, Megaptera novaeangliae. In view of the simplicity of the system, its effectiveness in acquiring multipurpose samples, and the apparently short-term disturbance it caused, it is recommended for future cetacean biopsy studies.

We examined blubber distribution in 50 mature harp seals (Phoca groenlandica) from the St. Lawrence River estuary, Canada, between December 1988 and April 1989. Blubber was thickest and most variable dorsally, becoming gradually thinner through the neck region and around the foreflippers. Blubber thickness relative to body radius was greatest dorsally at positions from 40 to 70% of standard length (measured back from the snout) and in the posterior region; it varied less topographically than blubber thickness alone, thereby increasing the insulating effectiveness of blubber stores. The largest sexual and seasonal differences in blubber were at the sites with the greatest relative blubber thicknesses. Pregnant females (winter) had thicker blubber than males (winter) or postpartum females (April) at corresponding body sites. Pregnant females had significantly thinner blubber ventrally in the abdominal region than at corresponding lateral positions, whereas males and postpartum females had a more uniform distribution. Blubber mass was highly correlated with estimated blubber volume (R2 = 0.9967, p 2 = 0.7847, p −3. We discuss the pattern of blubber distribution in harp seals with respect to the multiple functions of energy demands, thermal insulation, streamlining, and mobility.

We analysed the relationship of length to age in a sample of 204 harp seals collected in 1976–1979 and of 437 animals collected in 1988–1992, by fitting asymptotic growth curves. The only significant variations were in asymptotic length, which for 1988–1992 was significantly larger for males (170.4 cm) than for females (165.3 cm). This sexual dimorphism was not significant in 1976–1979, because the fitted asymptotic length of females varied greatly from year to year, being large in the 1976–1979 samples. An index of body condition (total weight/length2.6) and a volume index constructed by regressing body weight on length × axillary girth squared indicated that harp seals collected in 1988–1992 were in poorer condition than animals collected during 1976–1979. Although this suggests a decline in available resources, the possibility of differences arising from sampling bias cannot be excluded.

We examined the relationship between ringed seal body condition and reproduction and spring sea ice conditions in prime ringed seal habitat in Canada’s western Arctic during 1992 – 2011. Since 1970, ice conditions in east Amundsen Gulf and west Prince Albert Sound have shown only a slight trend toward earlier ice clearance (breakup) in spring (3 – 7 days per decade) ( p < 0.10) and no trend toward later freeze-up or increased variability in timing of spring ice clearance. A subsistence harvest – based sample of 2281 ringed seals was obtained during 1992 – 2011 from Masoyak, a traditional hunting camp located on the northwest shore of west Prince Albert Sound and less than 5 km from east Amundsen Gulf. The results revealed a statistically significant trend of decreasing mean annual body condition of ringed seals (using an index of length-mass-blubber depth [LMD]: adults, 0.14 m 1.5 /kg 0.5 /y; subadults, 0.24 m 1.5 /kg 0.5 /y) over the past two decades. A parallel result was that mean annual body condition of adults and subadults was correlated with the timing of fast ice clearance in spring (later ice clearance = worse condition). This correlation was most obvious in the extreme ice years in all sex/age groupings and was statistically significant for subadults. In mature females sampled since 1992, annual ovulation rates averaged 92.4 ± 16.3% (SD) and were greater than 80%, and mostly at 100%, in all years but two. Failure to ovulate was obvious in 2005, the most extreme late ice clearance year in our series, when only 30.0% of the mature adult females sampled ovulated. At the same time, values for seal body condition indices (adult females, LMD = 11.3; adult males, LMD = 12.4) and percent pups in the harvest (3.3%) were among the lowest recorded, and spring ice clearance was 38 d later than the 1992 – 2011 average. While this and previous studies indicate that the seal population in this core habitat has recovered from natural and extreme-year sea ice fluctuations over the past four decades, the potentially magnified effect of several consecutive extreme ice years, compounded by the concurrent decline in seal body condition that we have now detected over the past 20 years, is of particular concern.

In a study examining the range, distribution, and habitat use of the ringed seal, Phoca hispida , in Canada’s Western Arctic, eight ringed seals were live-captured, instrumented with satellite-linked (SLTDR-16) transmitters, and released at Cape Parry, Northwest Territories, Canada, on 17 – 19 September 2001 and 7 – 8 September 2002. Locations accepted by the filtering process were received from seven of the eight tagged seals (5 subadults, 1 adult female, 1 pup) over periods ranging from 35 to 207 days (mean 99 d, SD 66). Mean rates of travel were 0.91 m/s (SE 0.011, n = 7) in the Canadian Beaufort Sea, 0.92 m/s (SE 0.014, n = 7) offshore of Alaska’s North Slope, and 0.79 m/s (SE 0.008, n = 5) in the Chukchi Sea. On average, the seals took 32 days (range 19 – 56 d) to migrate between Cape Parry and Point Barrow, almost always remaining within 100 km of shore and over the continental shelf or slope, and covering an average migration distance of 2138 km. Dive depths for all groupings were mainly in the 4 – 80 m range (adult female: 63 – 73%; subadults: 54 – 73%; pup: 64 – 82%), with only the adult female diving deeper than 80 m on occasion, mainly in the Canadian Beaufort Sea (15.1% of her dives). The subadults and pup dove mainly for more than 1 to 5 min (60% and 55%, respectively), while a large proportion of the adult female’s dives were longer (34% for > 1 to 5 min; 31% for > 5 to 8 min; 5.4% for > 8 min). The tracks of the westward migrating seals revealed a routing through three political jurisdictions (including oil and gas industry lease areas in all three) over a period of about two months. This pattern highlights the importance of cooperation between the United States, Canada, and Russia in managing this species.

Belugas, Delphinapterus leucas, move into the coastal waters of Somerset Island as soon as the annual land-fast ice breaks up in late June – early July. Six bays or inlets which receive the outflow of rivers are the major areas of summer aggregation. Belugas captured and equipped with satellite-linked UHF transmitters in Cunningham Inlet (Barrow Strait), Elwin Bay (Prince Regent Inlet), and Creswell Bay moved west into Peel Sound where they frequented two other estuaries. Rapid and directed movement out of Peel Sound occurred in late August. All of the animals which transmitted locations into September or October moved to eastern Devon Island and Jones Sound. The longest period of transmission was 75 d, lasting until mid-October. Belugas tagged in three different locations around Somerset Island in the summers of 1988–93 showed a well-defined and consistent pattern of behaviour. Aerial surveys done during this period confirm that the vast majority of belugas in this region are involved in these seasonal movements.

We evaluated organochlorine contaminant concentrations and burdens in blubber samples from 50 harp seals (Phoca groenlandica) obtained from the estuary and northern Gulf of St. Lawrence and Hudson Strait, Canada, between December 1988 and December 1989. The concentration and burden of PCBs increased significantly during the winter months for males occupying the St. Lawrence estuary. The potential for rapid accumulation of contaminants in the estuary was also observed among females: nine postpartum females (1 month after weaning) had higher organochlorine levels than prepartum females from the same location. The lowest observed contaminant concentrations and burdens were in seals from Hudson Strait in autumn. In winter specimens, males had DDT and PCB concentrations about 4 and 2 times as great, respectively, as females of similar age distribution and collection date. Congeners with IUPAC Nos. 138 and 153 accounted for more than 50% of total identifiable PCBs, which is consistent with their prevalence in other marine biota. The concentration of PCBs has declined and the percent p,p′-DDE of total DDT has increased between 1982 and the present study. Unlike the beluga whale (Delphinapterus leucas), harp seals occupy the more polluted waters of the estuary only seasonally, and this may account for their lower residue concentrations.

Acute mountain sickness (AMS) is a common and disabling condition that occurs in healthy individuals ascending to high altitude. Based on the ability of iron to influence cellular oxygen sensing pathways, we hypothesized that iron supplementation would protect against AMS. To examine this hypothesis, 24 healthy sea-level residents were randomized to receive either intravenous iron(III)-hydroxide sucrose (200 mg) or saline placebo, before ascending rapidly to Cerro de Pasco, Peru (4340 m). The Lake Louise scoring system was used to assess incidence and severity of AMS at sea level and on the first full day at altitude. No significant difference in absolute AMS score was detected between the two groups either at baseline or at high altitude. However, the mean increase in AMS score was 65% smaller in the iron group than in the saline group (p

We evaluated body condition in 315 harp seals (Phoca groenlandica) obtained between 1988 and 1991. Total percent lipid of blubber did not vary between the five body sites and three depths sampled. In nine winter specimens, blubber, carcass, viscera, and skin contributed 89.5, 8.7, 0.9, and 0.9% of total body lipid. Pregnant females in winter had higher percent lipid in muscle than males, but no difference was observed in percent lipid in liver or blubber or in liver mass. Those females obtained 1 mo postpartum had the highest percent lipid in muscle and liver, the heaviest livers, but the lowest blubber lipid content. Sculp mass (skin with attached blubber) increased from autumn through late winter, with pregnant females having heavier sculps than males in winter. Both sculp and core mass varied on a seasonal and annual basis in males and females. Blubber was most variable dorsally between 40 and 70% of length, measured from the snout, and thickest at 50%, coincident with the position of maximum girth. Blubber thickness measured over the sternum was significantly less variable than at the 50% dorsal position. The direct measurements of body component masses may be necessary to detect subtle differences in body condition.

Of 247 harp seal (Phoca groenlandica) stomachs collected between December 1988 and October 1990 from western Hudson Strait (autumn), the northern Gulf of St. Lawrence (December), the St. Lawrence estuary (winter and April), and the Magdalen Islands (March), 140 (57%) contained food. The Magdalen Islands sample contained significantly more empty stomachs (62%, n = 164) than those from all other locations. Both the unreconstructed mass of stomach contents and the proportion of fish and invertebrate prey within individual stomachs varied significantly with location and season. Harp seals obtained from the northern Gulf of St. Lawrence during their southward migration fed less intensively, and on a wider variety of both invertebrate and fish prey, notably Parathemisto libellula, Pandalus sp., sand lance (Ammodytes sp.), and Atlantic cod (Gadus morhua). Feeding was more intensive and specialized in Hudson Strait and the St. Lawrence estuary where capelin (Mallotus villosus) dominated in the diet. Capelin contributed 89 and 98% of gross energy in samples from Hudson Strait (1990) and the estuary (April). The number of capelin per stomach consumed by seals from the St. Lawrence estuary in April was high (169.4 ± 58.9, mean ± SD, n = 9). The mean estimated lengths of capelin and cod consumed were 132 and 140 mm.

We describe scaling of morphological variables that influence total insulation in eight species of marine mammals ranging in average size from 35 to 30000 kg. We also calculate total heat loss and the partitioning of heat loss through the body surface and appendages. For the eight species investigated, heat loss in 0°C water is appreciably higher than the predicted basal metabolic rates for small species such as the ringed seal. Rorquals, on the other hand, will probably not need to raise their metabolic rates to keep warm. At rest, 10–30% of the heat production of a resting animal is lost through flippers, fins and flukes. This amount can increase to 70–80% during moderate exercise. Whole-body conductance scales with body size in the same way in marine as in terrestrial mammals, although conductance is higher for a given body size in a marine mammal.

Golgi-stained material of cerebellar cortices from 17 species was examined by measuring the fractal dimensions of the borders of Purkinje cells, which is a quantitative, objective measure of morphological complexity. Nine species (from birds to man) were chosen for a comparison with ANOVA and no statistically significant differences were found in their fractal dimensions. In contrast, a wide range of differences was found in the membrane areas across species lines. The Sholl coefficient, a measure of branch formation and temination and termination away from the soma, showed no consistent pattern for each cell. We interpret our results as indicating a constancy in morphological cellular complexity of Purkinje cells during late evolutionary time. © 1993 Wiley-Liss, Inc.

Prolyl hydroxylases are members of the iron- and 2-oxoglutarate-dependent dioxygenase enzyme family. Collagen prolyl hydroxylase is well known for its involvement in scurvy, in which ascorbate deficiency inhibits the enzyme and results in characteristic signs of the disease. Several distinct prolyl hydroxylases that hydroxylate (and thereby regulate) the hypoxia-inducible factor (HIF) transcription factors were discovered in 2001. These HIF prolyl hydroxylases, termed prolyl hydroxylase domain enzymes (PHDs), are the subject of this forum. HIF coordinates the cellular response to hypoxia, and the PHDs have attracted widespread interest as potential therapeutic targets in a wide range of diseases including anemia, ischemic heart disease, stroke, cancer, and pulmonary hypertension. Novel PHD-based pharmaceutical agents are now undergoing clinical trials. As well as original data, this forum includes reviews discussing recent advances in the biochemistry and therapeutic manipulation of PHDs, the potential role of PHD inhibitors in neuroprotection, and the involvement of PHDs in the complex interaction between oxygen homeostasis and iron homeostasis.

The hypoxia-inducible factor (HIF) family of transcription factors directs a coordinated cellular response to hypoxia that includes the transcriptional regulation of a number of metabolic enzymes. Chuvash polycythemia (CP) is an autosomal recessive human disorder in which the regulatory degradation of HIF is impaired, resulting in elevated levels of HIF at normal oxygen tensions. Apart from the polycythemia, CP patients have marked abnormalities of cardiopulmonary function. No studies of integrated metabolic function have been reported. Here we describe the response of these patients to a series of metabolic stresses: exercise of a large muscle mass on a cycle ergometer, exercise of a small muscle mass (calf muscle) which allowed noninvasive in vivo assessments of muscle metabolism using 31 P magnetic resonance spectroscopy, and a standard meal tolerance test. During exercise, CP patients had early and marked phosphocreatine depletion and acidosis in skeletal muscle, greater accumulation of lactate in blood, and reduced maximum exercise capacities. Muscle biopsy specimens from CP patients showed elevated levels of transcript for pyruvate dehydrogenase kinase, phosphofructokinase, and muscle pyruvate kinase. In cell culture, a range of experimental manipulations have been used to study the effects of HIF on cellular metabolism. However, these approaches provide no potential to investigate integrated responses at the level of the whole organism. Although CP is relatively subtle disorder, our study now reveals a striking regulatory role for HIF on metabolism during exercise in humans. These findings have significant implications for the development of therapeutic approaches targeting the HIF pathway.

From about mid-July to mid-August belugas (Delphinapterus leucas) over five seasons spent from 27 to 38 days at Cunningham Inlet (74°05′N, 93°45′W), where maximum numbers in each of eight seasons varied from 762 to 1741. While in the estuary, whales actively rub all their skin surface on the mud, pebble, and sharp limestone substrate near shore. Rubbing behaviour is more frequent early in the period of estuarine occupation and is exhibited by all age-classes with the exception of neonates and their dams. Remains of skin found in the area are proof that the epidermal surface is cut and shed from the whales in the shallow areas of the inlet. Active abrasion of skin surfaces softened by exposure to warm fresh water is thought to accelerate the moult, which is linked to a seasonal endocrine cycle and synchronized to meet the energetic demands imposed by their environment.

Odorous substances of rutting male ringed seals (Phoca hispida) were studied by extracting facial skin, which contains hypertrophied sebaceous and apocrine sweat glands, with methanol/hexane, and analysing the extracts with gas chromatography and combined gas chromatography/mass spectrometry. The extract contained high concentrations of a tertiary amine, three aminoalcohols, several organosulphur compounds, and two hydrocarbons. We suggest that the ringed seal males use scent to mark the breathing holes and subnivean lairs within their territories. Some of the lipids in the extract were not found in extracts from sexually immature males, and these lipids may be important as vehicles for scent deposition.

Length of lactation, pup growth rate, and female weight loss in ringed seals (Phoca hispida) were estimated using cross-sectional data from the Canadian and Norwegian Arctic. At birth the pups had a standard length of 63.4 cm (SE = 1.3, N = 11) and weighed 5.4 kg (SE = 0.4, N = 6). Weaning occurred approximately 39 d (range 36–41 d) after birth at an estimated length of 88.4 cm (SE = 0.65, N = 96) and an estimated weight of 22.1 kg, resulting in an increase in length of 0.64 cm∙d−1 and a weight change of 0.43 kg∙d−1. Regression of female weight on the number of days after the nominal date of birth for each region indicated that the postpartum female weighed 81.2 kg and lost 0.64 kg∙d−1 (95% CI = ±0.20). During lactation, female weight declined by an estimated 32%, with much of the loss occurring from the blubber. Analyses of stomachs indicated that ringed seals supplemented stored energy reserves by feeding during lactation.

The weights of testes, prostate gland and baculum of ringed seal males were related to age, season and differences in body size. There was a significant seasonal variation in testes and prostate gland size of sexually mature males, with a maximum occurring in early April. There were no seasonal changes in prostate weight of immature males, but some of the older immatures had elevated testes weights in April. Testes weight was significantly correlated with lean body mass. The increase in testes size with increasing body weight was greater for seals six years of age or older than for younger males. We suggest that some testicular growth and a seasonal cycle in testes growth occur before the testes become functional endocrinologically. We also believe that the primary event leading to puberty in ringed seals is an age-dependent shift in metabolic processes, directing a larger percentage of available energy towards the reproductive organs.

Mature male ringed seals (Phoca hispida) have a very strong odour emanating from the facial region during the breeding season. The inner surface of the skin from the heads of three animals captured during the mating season revealed the distribution of closely packed, much enlarged sebaceous glands on the anterior muzzle skin and extending into the interorbital and postvibrissal regions. A histological study was made of facial skin from 22 animals of different ages and both sexes, taken from Svalbard, Norway, during the breeding season. In mature males the sebaceous glands on the face were 3–8 times larger in cross section and more actively secreting than glands on the neck. Melanin granules were concentrated in the sebum. These facial glands were also 2–10 times larger and more actively secreting than the facial glands of immature males, mature females, or immature females. The apocrine sweat glands on the face of mature males were also much larger and more active than those of the other groups. It was concluded that the greater size, secretory activity, and melanin production of the sebaceous glands of mature male ringed seals could account for the strong odour and dark colour that have been observed on the face in the breeding season. The enlarged and active apocrine sweat glands might also contribute to the odour. The facial skin of six dominant bull grey seals (Halichoerus grypus), killed during the breeding season, had sebaceous glands of intermediate size, but high activity and high melanin content in the sebum. Their apocrine sweat glands were very large and active, indicating that they also may have a role in sexual signalling.

We have investigated the relationships between percent blubber content and xiphostemal blubber thickness or girth-to-length ratios in ringed seal (Phoca hispida), harp seal (Phoca groeniandica), and grey seal (Halichoerus grypus). The blubber content was significantly correlated with blubber depths and girth-to-length ratios in all three species, in addition, we have developed an estimator for percent blubber content (the LMD-index) based on standard length (L, in meters), body mass (M, in kilograms), and on blubber thickness (d, in meters) measured at a defined position dorsally. From these variables the percent blubber content (B%) can be estimated by the expression B% = 4.44 + 5693 [Formula: see text], with a standard error of the estimate of three percentage units. This index also gave reasonable estimates for blubber content in three harbour seals (Phoca vitulina) and eight bearded seals (Erignatus harbatus).

Seasonal changes in body mass and body composition of ringed seals (Phoca hispida) from the Svalbard Islands are described. The blubber content of adult females decreased from a high of about 50% at the beginning of the pupping season in March–April to a low of 31% during moulting in June. In adult males, the blubber content decreased from 41% in March to 29% in June. By estimating an individual seal's body mass by 1 April from its standard body length, we calculated an average daily loss of body mass of 160 g/day in adult females and 100 g/day in adult males from the start of lactation to the middle of moulting. The blubber content of sexually immature seals was less in June and July than in April, but the seasonal changes were smaller than in adult seals. We found no evidence of significant changes in core mass in adult seals, and suggest that the seasonal body mass changes are mostly due to changes in body fat content.

Epidermal morphology and proliferation were examined in beluga whales during three phases of their annual cycle: spring migration from oceanic wintering grounds, summer occupation of estuaries in Hudson Bay, and return migration in fall. Incursion into relatively warm brackish water was associated with decreased thickness of the stratum externum and sloughing of a superficial layer of degenerative epidermal cells, changes that resulted in the loss of a distinctive yellow hue apparent over the dorsal body surface of whales examined during spring migration. Proliferation rate, determined by incorporation of tritiated thymidine in germinal cells, averaged 13.8–16.6% in all three seasons, but exceeded 20% in 7 of 16 whales examined in the estuaries; similarly high values were not observed during spring migration, and in only one of nine animals sampled in the fall. Average proliferation rate in 13 captive belugas was 14.2–16.6%, two to three times higher than any reported value for other cetaceans or terrestrial mammals. Epidermal turnover time in a single whale studied over a 6-week period was estimated to be 70–75 days, comparable to that in bottlenose dolphins, but indicating a much higher rate of cell migration. In estuaries, elevated temperature and low salinity are presumably responsible for accelerating turnover of superficial cells, and may contribute to elevated proliferation rates by stimulating blood flow to the germinal layer.

Satellite-linked time-depth recorders were deployed on 17 ringed seals in early summer in 1999, 2000, and 2010, near the Inuvialuit community of Ulukhaktok, Northwest Territories, Canada. The main objective was to investigate movements and diving behaviour of ringed seals in the Prince Albert Sound (PAS) and eastern Amundsen Gulf (EAG) regions in relation to season, sex, and age-class. Tags performed well on 16 of 17 tagged seals, with average tracking periods of 256 d (SD 69, range: 134 – 352). Adult and subadult ringed seals traveled considerable distances throughout the open water period (mean = 5844 km, range = 1232 – 9473 km), using vast home ranges during this season, shown with 90 Percent Volume Contours (90 PVC) averaging 122 854 km2 for subadults, 76 658 km2 for adult females, and 21 649 km2 for adult males . Overall, adults spent 69.5% of the observed open water days in foraging/resident mode and 22.8% in traveling mode. The majority (75%) of total observed foraging/resident time was spent in PAS and EAG. Eleven of 12 adults made forays outside EAG and PAS to distant areas, including Prince of Wales Strait (7 seals), Viscount Melville Sound (6), Minto Inlet (4), western Amundsen Gulf (4), and six other zones. During open water season, subadults spent 36.8% traveling and 51.4% foraging/ resident, also mainly in EAG and PAS (61%), but they all traveled to distant zones, eight in total. During winter, all tagged adult females, five of seven adult males, and three of four subadults returned to PAS and EAG to occupy winter home ranges that were on average 15% of the size of the open water home range (mean winter ranges = 1299 km2 for adult males, 3599 km2 for adult females, and 30 499 km2 for subadults). The mean size of the winter home ranges varied by as much as a factor of 10 among the three winters examined. Seal movements were most restricted during the winters with extensive fast ice (1999 – 2000 and 2010 – 11) and least restricted during the winter (2000 – 01) when fast ice did not form in EAG. In winter, adult females made more long, deep dives than either adult males or subadults.

Polar bears are seasonal breeders and typically mate from late March to early May. Implantation is, however, delayed until autumn, which can allow plasticity in the date of mating. As for other seasonal breeders, a rapid return to estrus after the loss of dependent offspring can be expected, even into the summer. A few earlier observations and dissections of dead animals suggest that polar bears are able to mate in summer. We report on a mating incident on 29 June 2014, the first documented mating this late in the season among wild polar bears. The female had lost her dependent cub during the period prior to the mating event. We speculate that she lost this cub late in the mating season, entered estrus and successfully mated in late June. Keywords: Polar bear; mating season; mating behaviour; Svalbard; Arctic. (Published: 2 March 2015) Citation: Polar Research 2015, 34 , 25786, http://dx.doi.org/10.3402/polar.v34.25786

We recorded an unusually warm period in early April 1979 along the coastline at the end of the Hall Peninsula on southeastern Baffin Island, Nunavut. Maximum temperatures remained at or above freezing for almost a week, and rain fell on our field camp on three consecutive days. In contrast, meteorological data collected from three nearby coastal stations (Brevoort Island, Cape Dyer, and Resolution Island) between 1950 and 1992 indicated that the mean minimum and maximum air temperatures for the month of April are normally 10-20°C cooler than the averages we recorded at our camp. Periodic warming to near freezing, probably due to the maritime influence of nearby open water in Davis Strait, occurs in this area in late March and early April, but not usually to the degree we observed. Between 1950 and 1992, additional similar rain events were recorded only twice at the coastal weather stations. In late March, we found slumped roofs over some ringed seal ( Phoca hispida ) birth lairs and others that had collapsed, probably because of four days of weather only slightly below freezing and heat generated by seals within the lairs. After the rain in April, we found subnivean lairs with melted roofs, and several snowdrifts that had previously contained lairs were completely washed away. Newborn pups were left lying on the bare ice, subject to thermoregulatory stress and vulnerable to significantly increased predation by polar bears ( Ursus maritimus ) and arctic foxes ( Alopex lagopus ). If the climate continues to warm in the Arctic, as is predicted, it is likely that rain will be more widespread during early spring. If that occurs, the premature removal of protection offered by subnivean birth lairs may expose young ringed seal pups to high levels of predation, which may negatively affect populations of ringed seals and the polar bears that depend on them for food.

The beluga whale ( Delphinapterus leucas ) and the bowhead whale ( Balaena mysticetus ) are seasonal migrants to Canada's Western Arctic, occupying summer range in the southeastern Beaufort Sea and Amundsen Gulf within the Inuvialuit Settlement Region (ISR). These whales also travel through United States (Alaskan) and Russian offshore waters, which include migration routes and overwintering areas for both species. The beluga has for centuries been an important food resource of the aboriginal people of the Mackenzie Delta. From 1990 to 1999, the annual subsistence harvest of beluga in the ISR averaged 111, while only two bowheads were landed during this same period. The minimum size of the Eastern Beaufort Sea beluga stock has been estimated at 32 453 whales. The total annual removal of beluga by subsistence hunters from the ISR and Alaska is estimated at 189 whales, which is less than 0.6% of the minimum estimate of stock size. This level of harvest is sustainable. Between 1848 and 1921, commercial whalers decimated the Bering Sea population of bowhead whales. The size of the population, based on 1993 data, is estimated at 8200 (95% estimation interval of 7200-9400), constituting more than 90% of the world's remaining bowheads. This population increased at a rate of 3.2% from 1978 to 1993, while sustaining a harvest of about 0.6% per year. To ensure the continued well-being of these whales and their habitats, it is recommended that existing monitoring programs, commitments, and co-management partnerships be nurtured and maintained.

Imagine the scene, Dave, strong, youthful and sharp-eyed, poised to leap off the bow of a swift-turning zodiac, hurl himself into the frigid Arctic waters, and deftly place a hoop-net over the head of a thrashing beluga whale. Each evening we would sit quietly on the cliffs, sharing the satisfaction of a good day's work .... The spectacle of the hundreds of belugas just below the bluff, rubbing in the shallows of Cunningham Inlet, made this one of Dave's favourite places. He was, after all, the one who had found out why belugas were there. ... Dave was the first to document that a whale could actually moult, in a peculiar kind of mammalian way. Dave started his research career as an assistant at the Arctic Biological Station, Fisheries and Oceans Canada, in Ste. Anne de Bellevue, Quebec, .... Dave was clear in his vision and goals. In 1973, he decided on graduate training. Riding a wave of powerful recommendations, he arrived at the University of Guelph .... Dave earned his Master's degree and Ph.D., both with honours. ... From the moment Dave arrived at the university until the day he left 21 years later, ... three of us worked together from the Arctic to the tropics, from Maritime Canada to Florida, from Holman Island to South America to Hawaii- observing, studying, documenting, learning. ... In 1993, Dave went to Mystic Marine Life Aquarium as Director of Research and Veterinary Services. While south of the Canadian border, his interests and involvement in Arctic research grew stronger than ever. ... By today's measure, 50 years is a disappointingly short life, but Dave never wasted a moment and accomplished much. ...

Standardized, hunter-based sampling of harvested beluga whales was initiated in the three main harvesting areas of the Mackenzie River delta (Shallow Bay, Kendall Island, Kugmallit Bay) in 1980 and near Paulatuk, Northwest Territories, in 1989. Standard length and sex of landed whales have been recorded for 90 to 110 belugas per year since 1980, and ages have been determined since 1988. Hunters select larger and older belugas; males outnumbered females 2.0 to 1 between 1980 and 1989, 3.0 to 1 between 1990 and 1999, and 3.6 to 1 between 2000 and 2009. Age classes younger than 10 growth layer groups (GLGs) were essentially absent from harvests both in the Delta and near Paulatuk. Asymptotic lengths, calculated using GLG counts from teeth of 839 males and 225 females sampled over 16 seasons (1989, 1993 – 2008), were 435.3 cm (SE 2.0) for males and 380.1 cm (SE 1.8) for females. Males were 14.5% longer than females. Belugas landed in the Delta and Paulatuk were mainly mature adults (by hunter selection). Mature belugas landed by Paulatuk hunters were younger and shorter than those taken in the Delta because of age and sex segregation in the hunting areas. There was no difference in the size-at-age relationships for belugas landed at Paulatuk vs the Delta. The linear trend in size-at-age indicated a decline of 0.08% (SE 0.038%) per year, or 1.75% over the 19 year time series. The 314 male belugas landed in the Delta between 2000 and 2007 showed statistically significant differences in blubber thickness among years, but only a slight downward trend over this short period. Mean blubber was thickest in 2002 and 2003 and thinnest in 2005. The thinness of belugas in 2005, and subtle changes in growth of the belugas over the time series, may reflect ecosystem changes that have reduced the availability or quality and quantity of their prey in recent years. Further research, including isotope and fatty acid profiling, would be helpful in substantiating the declining trend in growth and elucidating the causative factors.

The capture of beluga whales, Delphinapterus leucas , for instrumentation or tagging afforded the opportunity to collect blood, which was analyzed to evaluate the animals' health and gain information on basic physiological systems. Here, we report on hematological and plasma chemical constituents in samples obtained from 183 belugas, 55 of which were handled during attempts to apply tracking instruments. The other 128 samples were either drawn from live belugas captured for exhibit in zoological parks or research or obtained from the fresh carcasses of whales taken by Inuit hunters. The data span a 15-year period beginning in 1983 and represent various beluga stocks in the Canadian Arctic. The majority of the specimens were collected during the summer or estuarine phase of the belugas' annual cycle. Comparisons by age group, sex, stock, season, and year revealed significant differences in most of the cellular and chemical constituents examined. These results demonstrate some of the variability that might be encountered when examining a "random" selection of belugas at a particular location and time. Immature-sized whales had higher leucocyte counts, electrolyte concentrations, enzyme activity, total protein, albumin, hemoglobin, and some metabolites than older animals. Sex alone was associated with few hematological and plasma chemical differences. Seasonal variation in thyroid hormone activity was linked to marked environmental changes associated with the transition from cold oceanic waters to relatively warm estuaries. Two belugas recaptured 19 and 24 days after instrumentation showed changes in leucocyte counts, hematocrit, and a variety of plasma chemical constituents, some of which indicate inflammation and a likely physiological response to handling and tagging stresses.

Thirty years ago, at a meeting devoted to finding new directions for Arctic biological oceanography, it was suggested that marine mammals might some day be used as "educated" oceanographic sampling platforms. They are "educated" because, through millions of years of evolution, they have developed the ability to find and consume such prey as the arctic cod, Boreogadus saida, a keystone ... Arctic species that to this day has largely eluded the efforts of scientists who have tried to study it .... The ice-covered and ice-filled waters of the polar regions have thwarted the attempts of oceanographers to study the Arctic marine ecosystem. ... Arctic seals, whales, and polar bears have been studied much more intensively than organisms lower down in the marine trophic pyramid. Studies of bears and seals have shown that large inter-annual changes in productivity occur in certain regions of the Arctic .... Studies of higher vertebrates have resulted in some interesting recent attempts to apply the "top-down" modeling approach. Such modeling uses the energy requirements of bears, seals, and whales to estimate the energy flow through the ecosystem ... or to calculate the standing crops of upper trophic-level components ... of regional Arctic marine ecosystems. To date, this appears to be the most practical and workable means available, but the assumptions and quantitative uncertainties at various stages in the model make it a blunt tool. ... The advent of satellite-linked VHF and other satellite-based remote sensing has opened the doors to research on a large geographical scale and an intensive schedule of sampling, both essential to furthering our understanding of Arctic marine ecosystems. ... One of the most interesting results from studies to date is that belugas consistently go to certain deep water areas to feed, in some cases traveling great distances from the center of their summer distribution to do so. ... The first stage in satellite-telemetry studies of some Arctic marine mammal species is being completed. The seasonal movements and annual migrations of polar bears and belugas are becoming well known for many of the North American stocks .... The next major leap forward in the study of Arctic marine mammals will be to use them to their full potential as "educated" oceanographic sampling platforms [i.e. attempting to relate their distribution or behaviour to physical oceanographic parameters]. ...

Twenty-one adult belugas (8M, 13F) were live-captured and instrumented with satellite-linked transmitters in the summer and fall of 1996. Twelve were captured in estuaries along the coast of Somerset Island in July and nine were captured in September in Croker Bay, SE Devon Island. This paper reports on the summer and autumn movements and dive depths of these animals from late July 1996 until the last tags ceased transmitting in November 1996. Of the 12 captured in July, 11 provided data for 30-126 days (mean = 84 days). Most of the animals moved rapidly to southern Peel Sound, where they all spent the month of August, making frequent deep dives, some of which were to depths near or at the seabed of the Franklin Trench. The belugas also used several bays along the coast of Prince of Wales Island and another one on Melville Peninsula. They left southern Peel Sound between late August and early September and moved rapidly to the south coast of Devon Island, many using Maxwell Bay and Croker Bay for several days. All belugas instrumented in Croker Bay in September, as well as the summer-tagged individuals that were still transmitting, moved east and north along the south and east coasts of Devon Island, eventually reaching Jones Sound and north Baffin Bay. They used many bays along the east coast of Devon Island and dove to depths often exceeding 200 m in the surrounding waters. Fifteen of the tags continued to transmit during the period when belugas are normally observed migrating along the West Greenland coast (late September-early October). Only one of the tagged animals moved to Greenland waters in late September. The others remained in the area known in winter as the North Water. The autumn tracking results suggest that the North Water may harbour a larger winter population of belugas than was previously suspected.

Between 1992 and 1998, 869 ringed seals taken in the subsistence harvest in western Prince Albert Sound were sampled by two Inuvialuit seal monitors from Holman, Northwest Territories. Considering the 1992-98 data along with data from 1971-78, we found that the mean body-mass index (BMI) values for females (>= 7 yr) were significantly lower in 1974 than in all other years examined. At the same time, ovulation rates fell from 100% in 1971 and 1972 to lows of 42.9% (1974) and 64.3% (1975), with a return to 93.8% in 1976. Mature females that had ovulated had significantly higher BMI values than those that had not ovulated. In eastern Amundsen Gulf, 1974 was the most severe ice year on recent record, with the latest date of clearing of the landfast ice (6 September), the earliest date of new ice formation (4 October), and the fewest number of open water days (28 days). There were no years between 1992 and 1998 that compared to 1974 in reduced ovulation rates, reduced body condition, or severity of ice conditions. Between 1992 and 1998, mean BMI values for adult females and males were lowest in 1994 and highest in 1998, and all annual mean BMI values were between the extremes of the 1970s. This variation in condition in the 1990s did not coincide with a reduction in ovulation rates of mature females, which remained high (93.5-100%) from 1992 to 1998. In 1998, the landfast ice cleared 43 days earlier than the average clearing date for the 1990-98 period, apparently interrupting the lactation period for seal pups located at the periphery of the core breeding habitat. The apparent effects on growth and condition of unweaned pups came at a time when marine food appeared to be abundant and available to all age classes of ringed seals.

Stomachs of 134 ringed seals from West Svalbard (Kongsfjorden) and East Svalbard (drift ice) were examined. Twenty-four prey taxa were found. The most important items were arctic cod ( Boreogadus saida ), shrimp ( Pandalus borealis ), krill ( Thysanoessa inermis ) and the amphipod Themisto libellula . In spring young redfish ( Sebastes sp.) was an important food item; in summer seals fed on dense aggregations of krill in front of glaciers. Mysids, amphipod crustaceans and small size classes of coastal fish species were abundant in Kongsfjorden, but seals take them as secondary food items only. Key words: ringed seals, Phoca hispida , arctic food web, fjord ecology, Svalbard, prey taxa

We examined the stability of fast ice areas in western and northern Spitsbergen, the area north of Nordaustlandet, the bays and sounds of Hinlopen Stretet and the large area in the northern part of Storfjorden. NOAA satellite imagery from 1974 and 1988 and NOAA (AVHRR) imagery from 1980-87 were used to determine the dates of freeze-up and break-up. The number of days of fast ice present before the nominal birth date of ringed seal pups were computed for all major bays and fjords. Ice thickness was then computed from these data. Known prime breeding habitat in Svalbard is found in areas near glacier fronts in protected fjords and bays, where densities of birth lairs are 5.46 km?2, corresponding to a ringed seal female density of 2.6 km?2. Most of the ringed seal breeding habitat in Svalbard, however, consists of flat fjord ice where snow accumulation is rarely deep enough to permit birth lair construction. In these areas pups are often born in the open. Based on breathing hole densities, the density of adult females in the flat ice areas in the breeding period was estimated to 0.98 km?2. A preliminary estimate is that approximately 19,500 pups could be born annually in the fast ice of Svalbard. Annual recruitment could be quite variable given the unpredictable nature of the fast ice areas and the high predation mortality on newborn pups. Discrepancies between our calculated ringed seal production and numbers of seals required to feed the large polar bear population in the area signal cause for management concern.

Ringed seals Phoca hispida , the smallest of the marine arctic pinnipeds, are one of only two seal species in the world adapted to life in the land-fast sea ice. The habitat is characterized by a stable ice platform forming in early winter and lies at latitudes subject to extreme low temperatures. The small body size of adults and semi-altricial pups are an unusual adaptation to cold, allowing ringed seals to use shelters that they construct in the snow overlying their breathing holes. These small subnivean structures act to hide adults and pups from predators, especially polar bears, Ursus maritimus , and arctic foxes, Alopex lagopus . It appears that dry lanugal pups could withstand the arctic cold without shelter, but pups that have been wetted become hypothermic and require shelter to regain thermoneutrality. Since female seals actively swim away with their pups from attacks on their birth lairs by foxes and bears, both the physical and the thermal protection of alternate subnivean lairs are important for the survival of the neonate. Weddell seals, Leptonychotes weddelli , resident in the land-fast ice of the Antarctic, are the ecological counterpart of the ringed seal. Their large body size is typical of the usual cold adaptive strategy of other polar phocid seals. Key words: ringed seal, behaviour, development, physiology, adaptations, arctic winter, Phoca hispida