Summer distribution and habitat characteristics of fin whales (Balaenoptera physalus) and humpback whales (Megaptera novaeangliae) off Northeast Kodiak Island, Alaska

Abstract

Summer distributions of fin (Balaenoptera physalus) and humpback (Megaptera novaeangliae) whales were examined relative to bathymetry, oceanography, and zooplankton composition and density in Marmot and Chiniak Bays (Kodiak Island, AK) during 2002 and 2003. Habitat use and habitat partitioning were assessed using Monte Carlo and randomization tests, logistic regression analyses, and kernel density probability contours of high-use areas. Fin whales associated with deeper, cooler waters near areas of maximum slope and consistently used Marmot Bay. Fin whale spatial-temporal distribution likely coincided with Neocalanus copepod concentrations during early summer and adult euphausiids later in summer. Fin whale associations with Pseudocalanus copepods may relate more to that copepods' prevalence than to relevance as prey. Humpback whale site fidelity and association with shallow waters was evident in 2002, but not in 2003. Variability in humpback whale distribution was likely related to their exploitation of forage fish aggregations and threshold foraging needs. High densities of adult euphausiids may promote spatial overlap and shared resource use by fin and humpback whales. This mesoscale snapshot of a dynamic nearshore marine environment and the whales foraging there is an integral step toward identifying and characterizing important habitats for endangered fin and humpback whales.