Acoustic monitoring of large whales in deep waters north and west of the British Isles: 1996 - 2005 (original) (raw)

For ten years beginning 1 October 1996, the songs of blue, fin, and humpback whales (Balaenoptera musculus, B. physalus, and Megaptera novaeangliae) were monitored in twelve large overlapping regions north and west of Britain and Ireland, using bottom-mounted hydrophone arrays operated by the US Navy. The regions monitored cover a latitudinal range of approximately 2300 km, from 42°N to 63°N, an area of more than 1 million km 2. The objectives of this study were (1) to describe and quantify the seasonal occurrence of song of blue, fin, and humpback whales in 12 deep-water monitoring areas adjacent to the continental shelf break west of the British Isles, and (2) to identify any significant long-term trends in rates of acoustic detections of blue, fin, or humpback whales in these regions. This report provides a preliminary overview and summary of the data collected in this study. Further analyses of these data and comparisons with results of recent visual sighting surveys are planned. This study constitutes the most extensive survey of acoustic activity of large whales ever undertaken in the eastern north Atlantic, sampling more than one million square kilometres on a weekly basis for ten years. This work has demonstrated consistent presence of blue, fin, and humpback whales in regions and at times of year where they were not previously known to occur. The annual peak detection periods for all three species occurred during months when few visual cetacean surveys have been conducted in these areas due to poor weather conditions. Continued long-term collection of such data could enable detection of changes in whale populations. Coupled with data on oceanographic, meteorological, and productivity conditions, long-term acoustic monitoring data may yield new insights into how such environmental variables influence the distribution of whale populations in space and time.