Habitat preference of common minke whale (Balaenoptera acutorostrata) in Skjálfandi Bay, Iceland

Abstract

Anthropogenic activity has contributed to increased extinction rates, creating a need to monitor and conserve vulnerable species. Understanding the distribution and habitat preference of threatened species can identify crucial habitats, for which protection can improve the population size numbers.  Here, we investigate the habitat preference of the common minke whale, a rapidly declining yet understudied cetacean species. We analysed minke whale sightings over time and in relation to environmental factors (depth, sea surface temperature, sediment, chlorophyll), based on long-term monitoring data from Skjálfandi Bay in the northeast of Iceland. We found minke whales have a preference for water depth between 9-70m, and water temperature of either colder than 6°C or warmer than 9°C. Shallow depth was a strong predictor of minke whale presence, which matched sandeel distribution. Sandeels require shallow depths for spawning and overwinter burrowing, and the match between minke whale depth presence and sandeel habitat is in good agreement with sandeels being an important minke whale food source. Although the relationship between minke whale presence and sea surface temperature is weak, it also matched sandeel distribution. We also detected a decline in minke whale population size over the study period (2009-2018). The population decline observed here is consistent with the population trend estimated for the Icelandic population. We suggest that the habitat preferences identified here should be considered for conservation recommendations and minimising disturbance in the identified, crucial feeding areas.