Blue and fin whale call source levels and propagation range in the Southern Ocean

Abstract

Blue (Balaenoptera musculus) and fin whales (B. physalus) produce high-intensity, low-frequency calls, which probably function for communication during mating and feeding. The source levels of blue and fin whale calls off the Western Antarctic Peninsula were calculated using recordings made with calibrated, bottom-moored hydrophones. Blue whales were located up to a range of 200km using hyperbolic localization and time difference of arrival. The distance to fin whales, estimated using multipath arrivals of their calls, was up to 56km. The error in range measurements was 3.8km using hyperbolic localization, and 3.4km using multipath arrivals. Both species produced high-intensity calls; the average blue whale call source level was 189±3dB re:1μPa-1m over 25–29Hz, and the average fin whale call source level was 189±4dB re:1μPa-1m over 15–28Hz. Blue and fin whale populations in the Southern Ocean have remained at low numbers for decades since they became protected; using source level and detection range from passive acoustic recordings can help in calculating the relative density of calling whales.