Combining visual and fixed passive acoustic methods to measure annual variability of cetacean occurrence at the NE‐coast of Iceland.

Abstract

In order to measure cetacean occurrence at the NE‐coast of Iceland, two seabed‐mounted Ecological Acoustic Recorders (EARs) were deployed in Skjálfandi Bay in September 2008, deployments will continue throughout September 2010. To obtain species confirmation, visual observations were conducted from a lighthouse in October 2008 to September 2009 with total observation effort of 202 h. With visual observations, the aim was to acquire background information on the cetacean sighted in the area to improve the estimates of occurrence in continued long‐term passive acoustic recordings in Icelandic and adjacent waters. Movements and locations of the animals were recorded using a theodolite and a real‐time mapping program (CYCLOPS TRACKER). Visual observations included sightings of blue whales (Balenoptera musculus), Humpback whales (Megaptera novaeangliae), Minke whales (Balaenoptera acutorostrata), white‐beaked dolphins (Lagernorhynchus albirostris) and killer whales (Orcinus orca). A custom MATLAB program is used to automatically detect and analyze target biological sounds produced by cetaceans or by pelagic fish recorded on the EARs. The visual data are compared to the occurrence of identified sounds in order to better understand the vocal activity and average silence periods of the cetaceans. Also, detected vocalizations are compared to the number, location, and behavior of simultaneously sighted animals.