Using passive acoustics to model blue whale habitat off the Western Antarctic Peninsula

Habitat preferences of calling blue whales were investigated using data from two multidisciplinary oceanographic cruises conducted off the Western Antarctic Peninsula (WAP) during the austral falls of 2001 and 2002. Data were collected on depth, temperature, salinity, chlorophyll a (Chl-a) concentration, krill biomass, zooplankton abundance, and blue whale call presence. In 2001, the study area was sea ice free, high Chl-a concentrations occurred over a small area, krill biomass and zooplankton abundance were high, and few blue whale calls were detected. In 2002 the sea ice covered the southern part of the survey area, Chl-a was high over a large area, krill and zooplankton were low, and there were more blue whale calls. Logistic regression analysis revealed blue whale calls were positively correlated with depth and SST, and negatively correlated with the mean zooplankton abundance from 101 to 300 m and the mean krill biomass in the top 100 m. The negative correlation between blue whale calls and zooplankton could occur if feeding animals do not produce calls. Our survey area did not cover the full range of blue whale habitat off the WAP, as blue whales probably follow the melting and freezing ice edge through this region. Passive acoustics can provide insight to mesoscale habitat use by blue whales in the Southern Ocean where visual sightings are rare, but the ability to localize on the calling animals would greatly improve the ability to model at a finer scale.