We provide an exploratory description of the dive behavior of 23 beluga whales of the eastern Chukchi Sea stock, tagged with satellite-linked time and depth recorders at Point Lay, Alaska, between ...1998 and 2007. Because of differences in how transmitters were parameterized, we analyzed data from tags deployed from 1998 to 2002 (n = 20 tags) and data from tags deployed in 2007 (n = 3 tags) separately. Using cluster analysis, we found three basic dive types in the 1998—2002 dataset. "Shallow" diving behavior was characterized by dives mostly 50 m in depth. "Intermediate" diving behavior was characterized by having one mode near the surface and a second mode near 250 m. "Deep" diving behavior was characterized by having one mode near the surface and a second mode more than 400 m from the surface. The average number of dives per hour ranged from 5.1 (SD = 2.1) to 9.8 (SD = 2.9) across dive types, with the fewest dives per hour in the deep diving category. In general, duration of dives ranged from 1 to 18 minutes; however, dives up to 21 minutes occurred in the deepest diving category. We found little evidence that dive behavior of the belugas in our sample varied by sex or age. In general, belugas dove more deeply in the eastern Beaufort Sea than in the western Beaufort or Chukchi Seas. The depths to which belugas most commonly dive in Barrow Canyon and along the Beaufort shelf break (200—300 m) correspond to the boundary where colder Pacific water overlies warmer Atlantic water, which is probably where Arctic cod (Boreogadus saida) are most dense. Diving depths within the Arctic Basin suggest that belugas are foraging mostly within the warm layer of Atlantic Water (∼200—1000 m). Nous dressons une description exploratoire du comportement de plongée de 23 bélugas du cheptel de l'est de la mer des Tchouktches dotés de marqueurs d'enregistreurs satellitaires de profondeur temporelle à Point Lay, en Alaska, entre 1998 et 2007. En raison des différences de paramétrage des transmetteurs, nous avons analysé séparément les données de marqueurs déployés de 1998 à 2002 (n = 20 marqueurs) et les données de marqueurs déployés en 2007 (n = 3 marqueurs). Grâce à une analyse par grappes, nous avons trouvé trois types de plongée fondamentaux dans l'ensemble des données de 1998 à 2002. Le comportement de plongée « en eau peu profonde » était principalement caractérisé par des plongées de 50 m de profondeur. Le comportement de plongée « intermédiaire » était caractérisé par un mode de plongée près de la surface et un autre mode à près de 250 m. Le comportement de plongée « en profondeur » était caractérisé par un mode de plongée près de la surface et un deuxième mode à plus de 400 m de la surface. Le nombre moyen de plongées à l'heure variait de 5,1 (écart-type = 2,1) à 9,8 (écart-type = 2,9) pour ce qui est de tous les types de plongée, la catégorie des plongées en profondeur ayant enregistré le moins grand nombre de plongées. En général, la durée des plongées durait de 1 à 18 minutes, mais cela dit, certaines des plongées en profondeur ont duré jusqu'à 21 minutes. Nous avons trouvé peu d'indices portant à croire que le comportement de plongée des bélugas de notre échantillon variait en fonction du sexe ou de l'âge. De manière générale, les bélugas plongeaient plus en profondeur dans l'est de la mer de Beaufort que dans l'ouest de la mer de Beaufort ou dans la mer des Tchouktches. Les profondeurs auxquelles les bélugas plongent le plus souvent dans le canyon Barrow et le long du rebord continental de Beaufort (de 200 à 300 m) correspondent à la limite où l'eau plus froide du Pacifique se superpose à l'eau plus chaude de l'Atlantique, là où la morue polaire (Boreogadus saida) est plus dense. Dans le bassin arctique, la profondeur des plongées suggère que les bélugas s'alimentent surtout dans la couche tempérée d'eau de l'Atlantique (∼200 à 1000 m).
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Availability of summer sea ice has been decreasing in the Chukchi Sea during recent decades, and increasing numbers of Pacific walruses have begun using coastal haulouts in late summer during years ...when sea ice retreats beyond the continental shelf. Calves and yearlings are particularly susceptible to being crushed during disturbance events that cause the herd to panic and stampede at these large haulouts, but the potential population-level effects of this mortality are unknown. We used recent harvest data, along with previous assumptions about demographic parameters for this population, to estimate female population size and structure in 2009 and project these numbers forward using a range of assumptions about future harvests and haulout-related mortality that might result from increased use of coastal haulouts during late summer. We found that if demographic parameters were held constant, the levels of harvest that occurred during 1990–2008 would have allowed the population to grow during that period. Our projections indicate, however, that an increase in haulout-related mortality affecting only calves has a greater effect on the population than an equivalent increase in harvest-related mortality distributed among all age classes. Therefore, disturbance-related mortality of calves at coastal haulouts may have relatively important population consequences.
We collected blood from 18 beluga whales (Delphinapterus leucas), live-captured in Bristol Bay, Alaska, USA, in May and September 2008, to establish baseline hematologic and serum chemistry values ...and to determine whether there were significant differences in hematologic values by sex, season, size/age, or time during the capture period. Whole blood was collected within an average of 19 min (range=11–30 min) after the net was set for capture, and for eight animals, blood collection was repeated in a later season after between 80–100 min; all blood was processed within 12 hr. Mean hematocrit, chloride, creatinine, total protein, albumin, and alkaline phosphatase were significantly lower in May than they were in September, whereas mean corpuscular hemoglobin concentration, monocytes, phosphorous, magnesium, blood urea nitrogen, alanine aminotransferase, aspartate aminotransferase, γ-glutamyltranspeptidase, and creatinine kinase were significantly higher. Mean total protein, white blood cell count, neutrophils, and lymphocytes were significantly higher early in the capture period than they were later. No significant differences in blood analyte values were noted between males and females. Using overall body length as a proxy for age, larger (older) belugas had lower white blood cell, lymphocyte, and eosinophil counts as well as lower sodium, potassium, and calcium levels but higher creatinine levels than smaller belugas. These data provide values for hematology and serum chemistry for comparisons with other wild belugas.
We collated available satellite telemetry data for six species of ice-associated marine mammals in the Pacific Arctic: ringed seals (Pusa hispida; n = 118), bearded seals (Erignathus barbatus, ...n = 51), spotted seals (Phoca largha, n = 72), Pacific walruses (Odobenus rosmarus divergens, n = 389); bowhead whales (Balaena mysticetus, n = 46), and five Arctic and sub-arctic stocks of beluga whales (Delphinapterus leucas, n = 103). We also included one seasonal resident, eastern North Pacific gray whales (Eschrichtius robustus, n = 12). This review summarized the distribution of daily locations from satellite-linked transmitters during two analysis periods, summer (May–November) and winter (December–April), and then examined the overlap among species. Six multi-species core use areas were identified during the summer period: 1) Chukotka/Bering Strait; 2) Norton Sound; 3) Kotzebue Sound; 4) the northeastern Chukchi Sea; 5) Mackenzie River Delta/Amundsen Gulf; and 6) Viscount Melville Sound. During the winter period, we identified four multi-species core use areas: 1) Anadyr Gulf/Strait; 2) central Bering Sea; 3) Nunivak Island; and 4) Bristol Bay. During the summer period, four of the six areas were centered on the greater Bering Strait region and the northwestern coast of Alaska and included most of the species we examined. The two remaining summer areas were in the western Canadian Arctic and were largely defined by the seasonal presence of Bering-Chukchi-Beaufort stock bowhead whales and Eastern Beaufort Sea stock beluga whales, whose distribution overlapped during both summer and winter periods. During the winter period, the main multi-species core use area was located near the Gulf of Anadyr and extended northwards through Anadyr and Bering Straits. This area is contained within the Bering Sea “green belt”, an area of enhanced primary and secondary productivity in the Bering Sea. We also described available telemetry data and where they can be found as of 2017. These data are important for understanding ice-associated marine mammal movements and habitat use in the Pacific Arctic and should be archived, with appropriate metadata, to ensure they are available for future retrospective analyses.
was first isolated from true seals in 1994 and from eared seals in 2008. Although few pathological findings have been associated with infection in true seals, reproductive pathology including ...abortions, and the isolation of the zoonotic strain type 27 have been documented in eared seals. In this study, a
enzyme-linked immunosorbent assay (ELISA) and the Rose Bengal test (RBT) were initially compared for 206 serum samples and a discrepancy between the tests was found. Following removal of lipids from the serum samples, ELISA results were unaltered while the agreement between the tests was improved, indicating that serum lipids affected the initial RBT outcome. For the remaining screening, we used ELISA to investigate the presence of
antibodies in sera of 231 eared and 1,412 true seals from Alaskan waters sampled between 1975 and 2011. In eared seals,
antibodies were found in two Steller sea lions (
) (2%) and none of the 107 Northern fur seals (
). The low seroprevalence in eared seals indicate a low level of exposure or lack of susceptibility to infection. Alternatively, mortality due to the
infection may remove seropositive animals from the population.
antibodies were detected in all true seal species investigated; harbor seals (
) (25%), spotted seals (
) (19%), ribbon seals (
) (16%), and ringed seals (
) (14%). There was a low seroprevalence among pups, a higher seroprevalence among juveniles, and a subsequent decreasing probability of seropositivity with age in harbor seals. Similar patterns were present for the other true seal species; however, solid conclusions could not be made due to sample size. This pattern is in accordance with previous reports on
infections in true seals and may suggest environmental exposure to
at the juvenile stage, with a following clearance of infection. Furthermore, analyses by region showed minor differences in the probability of being seropositive for harbor seals from different regions regardless of the local seal population trend, signifying that the
infection may not cause significant mortality in these populations. In conclusion, the
infection pattern is very different for eared and true seals.
The monodontids--narwhals, Monodon monoceros, and belugas, Delphinapterus leucas--are found in much of the Arctic and in some subarctic areas. They are hunted by indigenous subsistence users. In the ...past, some populations were substantially reduced by commercial hunting and culling; more recently, some populations have declined due to uncontrolled subsistence hunting and environmental degradation. Monodontids are impacted increasingly by human activities in the Arctic including ship and boat traffic, industrial development, icebreaking, seismic surveys, competition with fisheries, and alteration of habitat due to climate change. Since comprehensive reviews in the 1990's, substantial new information has become available on both species and on changes to their habitat as a result of human activities and climate change. Thus NAMMCO and partners undertook an updated review in 2017. The review recognized 21 extant beluga stocks, 1 extirpated beluga stock, and 12 stocks of narwhals. The available information on each stock regarding population size, depletion level, current and past removals, and trends in abundance was reviewed to determine status. Concern was expressed where the lack of information prevented reliable assessment, removals were thought to be unsustainable, or the population was deemed at risk of declining even without direct removals by hunting. Beluga stocks of greatest concern are the small stocks in Ungava Bay (possibly extirpated), Cook Inlet (ca 300), St. Lawrence Estuary (ca 900), and Cumberland Sound (ca 1,100), and the stocks with uncertainty in Eastern Hudson Bay and the Barents-Kara-Laptev Seas. Narwhal stocks of greatest concern are those in Melville Bay and East Greenland.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Bowhead whales (Balaena mysticetus) of the western Arctic stock winter in ice‐covered continental shelf regions of the Bering Sea, where pot fisheries for crabs (Paralithodes and Chionoecetes spp.) ...and Pacific cod (Gadus macrocephalus) pose a risk of entanglement. In the winter of 2008–2009 and 2009–2010 the spatial distribution of 21 satellite tagged bowhead whales partially overlapped areas in which pot fisheries for cod and blue king crab (Paralithodes platypus) occurred. However, these fisheries ended before whales entered the fishing areas, thus avoiding temporal overlap. A fishery for snow crab (Chionoecetes opilio) typically runs from January to May and provides the greatest potential for bowhead whales to encounter active pot gear. Tagged whales did not enter the area of the snow crab fishery during this study and generally remained in areas with >90% sea ice concentration, which is too concentrated for crab boats to penetrate. Pack ice sometimes overruns active fishing areas, resulting in lost gear, which is the most likely source of entanglement. The western Arctic stock of bowhead whales was increasing as of 2004; as such, incidental mortality from commercial pot fisheries is probably negligible at this time. Regardless, entanglement may increase over time and should be monitored.
•Ringed seals ⩾1year of age are eating more (%FO) Arctic cod (Boreogadus saida).•Ringed seals are growing faster, have thicker blubber, and females mature earlier.•Ringed seal growth and the ...proportion of pups harvested decreased with heavier ice.•Bearded seals ⩾1year of age are eating fewer (%FO) invertebrates (10 of 24 taxa).•Bearded seals have thicker blubber and females mature earlier now.
Reductions in summer sea ice in the Chukchi and Beaufort seas are expected to affect what has been an ice-adapted marine food web in the Pacific Arctic. To determine whether recent decreases in sea ice have affected ice-associated marine predators (i.e., ringed, Pusa hispida, and bearded seals, Erignathus barbatus) in the Bering and Chukchi seas we compared diet, body condition, growth, productivity, and the proportion of pups harvested (an index of weaning success) for seals of each species harvested by 11 Alaskan villages during two periods; a historical (1975–1984) and a recent period (2003–2012). We also examined how changes in indices of seal health may be correlated with the reduction of sea ice characteristic of the recent period. For ringed seals ⩾1year of age, the % frequency of occurrence (%FO) of Arctic cod (Boreogadus saida), walleye pollock (Gadus chalcogramma), rainbow smelt (Osmerus mordax), and Pacific herring (Clupea pallasi) increased from the historic to the recent period, while the %FO of invertebrates decreased for both pups and seals ⩾1year of age. For bearded seals ⩾1year of age, the %FO of Arctic cod, pricklebacks, and flatfish increased during the recent period, while the %FO of saffron cod (Eleginus gracilis) decreased for pups. Although invertebrates did not change overall for either age class, decreases occurred in 10 of 24 specific prey categories, for bearded seals ⩾1year of age; only echiurids increased. The %FO of gastropods and bivalves increased for pups while isopods and one species of shrimp and crab decreased in occurrence.
During the recent period ringed seals grew faster, had thicker blubber, had no change in pregnancy rate, matured 2years earlier, and a larger proportion of pups was harvested than during the historical period. Correlations with spring ice concentration showed that the growth and blubber thickness of seals ⩾1year of age, blubber thickness of pups, and the proportion of pups in the harvest all declined for ringed seals when ice concentrations were higher in the historic period. However, only the correlations between high ice concentrations and growth of ringed seals ⩾1year of age and the proportion of ringed seal pups in the harvest were statistically significant. Although growth of bearded seals ⩾1year of age was slower during the recent period, it was similar to the average over the entire time series, and blubber thickness increased. Pup growth and blubber thickness did not change between periods. There was no change in pregnancy rate, but females matured 1.6years earlier, and a larger proportion of pups were harvested. Correlations with spring ice concentration showed that the growth of seals ⩾1year of age, the growth of pups, blubber thickness of pups, and proportion of pups in the harvest also declined for bearded seals when sea ice concentrations were higher. However, no relationships between bearded seals and sea ice were statistically significant. Overall, our results suggest that ringed seals in the Alaskan Bering and Chukchi seas have adjusted to changes in diet, are growing faster and possibly weaning more pups in the recent compared to the historic period. These patterns are less evident for bearded seals. Although the ringed and bearded seals we examined have not exhibited the declines in body condition, growth, or reproduction observed in other populations, continued monitoring and comparison among seal populations is vital to understanding the effects of changing environmental conditions in the Pacific Arctic region.
PDF
