Cetacean Habitat Selection in the Alaskan Arctic during Summer and Autumn

Abstract

ABSTRACT. Ten years of sighting data from aerial surveys offshore of northern Alaska were analyzed to investigate seasonal variability in cetacean habitat selection. Distinct habitats were described for bowhead whales (Balaena mysticetus), white whales (Delphinapterus leucas), and gray whales (Eschrichtius robustus) on the basis of habitat selection ratios calculated for bathymetric and ice cover regimes. In summer, bowheads selected continental slope waters and moderate ice conditions; white whales selected slope and basin waters and moderate to heavy ice conditions; and gray whales selected coastal/shoal waters and open water. In autumn, bowheads selected inner shelf waters and light ice conditions; white whales selected outer shelf and slope waters and moderate to heavy ice; and gray whales selected coastal and shoal/trough habitats in light ice and open water. Habitat differences among species were significant in both seasons (ANOVA F > 28, p < 0.00001). Interseasonal depth and ice cover habitats were significantly different for bowhead whales (p < 0.00002), but not for gray whales (p > 0.35). White whale depth habitat was significantly different between seasons (p < 0.00002), but ice cover habitat was not (p < 0.08).Key words: Alaska, Arctic, Beaufort Sea, bowhead whale, Chukchi Sea, gray whale, habitat selection, white whale RÉSUMÉ. Des données d'observation réalisées sur dix années (1982 -1991) grâce à des relevés aériens au large de l'Alaska septentrional ont été analysées dans le cadre de recherches sur la variabilité saisonnière dans la sélection de l'habitat des cétacés. On a décrit des habitats distincts pour la baleine boréale (Balaena mysticetus), la baleine blanche (Delphinapterus leucas) et la baleine grise de Californie (Eschrichtius robustus) en se fondant sur les taux de sélection de l'habitat calculés pour le régime bathymétrique et celui de la couverture de glace. En été, la baleine boréale choisissait les eaux de la pente continentale et des conditions de glace modérée; la baleine blanche choisissait les eaux de la pente continentale et du bassin océanique, et des conditions de glace allant de modérée à épaisse; et la baleine grise choisissait des eaux côtières et de hauts-fonds ainsi que l'eau libre. En automne, la baleine boréale choisissait les eaux intérieures du plateau continental, où se trouvait une faible concentration de glace; la baleine blanche choisissait les eaux à l'extérieur du plateau et sur la pente, ainsi qu'une glace allant de modérée à épaisse; et la baleine grise choisissait des habitats côtiers et de hauts-fonds ou des fossés à faible concentration de glace et à eau libre. Les différences d'habitat entre les espèces étaient importantes durant les deux saisons (ANOVA F > 28, p < 0,00001). D'une saison à une autre, les habitats différaient sensiblement quant à la profondeur et à la couverture de glace pour la baleine boréale (p < 0,00002), mais pas pour la baleine grise (p > 0,35). La profondeur de l'habitat pour la baleine blanche variait sensiblement d'une saison à u...

Water mass and bathymetric characteristics of polar cod habitat along the continental shelf and slope of the Beaufort and Chukchi seas

“…It is common in the pelagic zone, at ice edges and also the epontic zone (the area near the undersurface of ice) where it preys upon fauna in the ice algae community (Bradstreet and Cross 1982;Bradstreet et al 1986;Crawford andJorgenson 1990, 1993;Gradinger et al 2005). Physical irregularities at the ice edge may represent cryptic habitat for these Wsh, places where they can hide from a wide variety of predators (Bradstreet and Cross 1982;Lønne and Gulliksen 1989;Moore et al 2000;Gradinger and Bluhm 2004). Early life stages are predominantly in layers of zooplankton drifting beneath the ice and in open water (Sekerak 1982;Bradstreet et al 1986;Crawford and Jorgenson 1990;Fortier et al 2006).…”

“…Because beluga feed primarily on polar cod (Bradstreet et al 1986), their feeding areas indicate the location of concentrations of the Wsh (Harwood and Smith 2002). Aerial surveys Xown in the western Arctic during September in the 1980s and 1990s yielded sightings of belugas on the outer portion of the Mackenzie Shelf and on (Clarke et al 1993;Moore et al 2000;Richard et al 2001). More recent studies monitoring movements of tagged belugas also showed them following the slope region (Richard et al 2001) where we detected Wsh near the bottom (200-350 m).…”

Offshore Distances of Bowhead Whales (<i>Balaena mysticetus</i>) Observed during Fall in the Beaufort Sea, 1982–2000: An Alternative Interpretation

“…The U.S. Department of the Interior has sponsored spring and fall aerial surveys of bowhead whales in the Beaufort Sea for monitoring purposes since 1979 (Treacy, 2002), and the present research is considered a follow-up to previous work (Moore and Clarke, 1992;Moore and Reeves, 1993;Moore and DeMaster, 1997;Moore, 2000;Moore et al, 2000). One goal of the current monitoring project is to describe distribution and movement patterns of bowhead whales in the fall, when they migrate westward across the Alaskan Beaufort Sea.…”

“…Here, we include analysis of offshore distance of bowhead whales encountered during fall surveys and describe the pattern of bowhead distribution as a function of annual sea-ice conditions. The extensive aerial survey database that we analyzed overlaps somewhat that analyzed by Moore (2000), Moore et al (2000), and others (1982 -91), but our analysis includes more recent information (1992 -2000) and an alternative interpretation of the data.…”

The Barents and Chukchi Seas: Comparison of two Arctic shelf ecosystems

“…Beluga whales (Delphinapterus leucas) spend part of the summer in the Chukchi Sea, though most migrate through the Chukchi to summering areas that are located to the east (Carroll et al, 1987;Moore et al, , 2000. Similarly, bowhead whales, for the most part, migrate through the Chukchi Sea with little or no feeding in spring.…”