Calls recorded from North Pacific right whales (Eubalaena japonica) in the eastern Bering Sea

Résumé

Calls from North Pacific right whales (Eubalaena japonica) were recorded in the eastern Bering Sea during a visual and acoustic survey aboard the US Coast Guard buoy tender Sweetbrier, in July 1999. Calls were commonly detected to 20km, and in one case approximately 30km, via deployment of arrays of directional sonobuoys. Acoustic detections (clusters of right whale calls separated by time and location) numbered 26, but only five right whales were seen. Only one right whale produced calls while under visual observation. The types of calls recorded from North Pacific right whales were similar in duration and frequency to calls recorded from right whales in the South Atlantic. The predominant call type (85%; 436 of 511 calls) was the ‘up’ call, a signal sweeping from about 90Hz to 150Hz in 0.7s. Two call types are described as ‘down’ and ‘constant’ calls, based upon nomenclature established for southern right whales (Eubalaena australis). One call type, the ‘down-up’ was unique to the North Pacific repertoire. Right whales commonly produced calls in series lasting several minutes and then became silent for an hour or more, with some animals not calling for periods of at least four hours. Other cetaceans detected acoustically by ‘random’ sonobuoy deployments during the cruise included fin whales (19 times), killer whales (3 times) and sperm whales (once).