Recent ecological insights into the endangered Cook Inlet beluga via acoustic monitoring

Abstract

The endangered Cook Inlet beluga population is non-migratory and located in south-central Alaska. Estimated at <300 individuals, it is declining more rapidly than previously thought. The Recovery Plan highlights a paucity of information on basic ecology impeding proper management decisions. The Alaska Department of Fish and Game and the National Marine Fisheries Service are collaborating on a passive acoustics monitoring program to address crucial information gaps. Year-round seasonal distribution and feeding occurrence is described for key areas within the critical habitat. Acoustic detections are greater in the upper inlet during summer, peaking in known concentration areas. Foraging peaks coincide with the presence of various anadromous fish runs from spring to fall. Low levels of feeding activity in winter suggest a lack of feeding aggregations in these areas. Thirteen sources of anthropogenic noise occur within the critical habitat, many exceeding behavioral harassment levels. Using a case-controlled approach in which periods with and without anthropogenic noise were compared, a significant negative correlation between noise levels and vocalization detections was found, However, masking by flow noise due to the strong currents in Cook Inlet might be affecting these results more than a true behavioral response. Further research remains ongoing to confirm/reject this hypothesis.