The target strength of the northern right whale (Eubalaena glacialis)

The greatest cause of anthropogenic mortality in great whales is ship strikes. Avoiding collisions, which are almost exclusively with baleen whales, may be critical to the survival of the northern right whale (Eubalaena glacialis). A potential solution to this problem is the use of an active forward‐looking obstacle avoidance sonar. This sonar could alert the ship’s crew of the presence of the whales or other obstacles at useful maneuvering ranges. The prediction of these detection ranges depends on the reflectivity of the whales. The focus of this study is the determination of target strength of the right whale. In May and September of 1998, a prototype phased‐array sonar was mounted on the bow of a 25‐m research vessel to collect these measurements. The sonar used a CW ping with a frequency of 87 kHz, a duration of 2 ms, a source level of 175 dB re: 1 μPa at 1 m. The receive array consisted of an 8×8 element array with BD wavelength spacing. The frequency was chosen to be inaudible to the baleen whales. Target strengths were also collected for humpback whales (Megaptera novaeangliae), and compare well with previously published data. [Work supported by NMFS and NSF.]