Target strengths of humpback whales Megaptera novaeangliae

Abstract

Measurements of the target strengths of humpback whales, Megaptera novaeangliae, have been made at short range. The use of a perfectly reflecting model has enabled the results obtained to be extrapolated to long ranges. The target strength at infinite range of adult humpbacks about 15 yd in length, insonified at 20 kHz, was found to be + dB, near the side aspect, and − 4 dB, near the head aspect. A juvenile humpback about 10 yd in length, insonified at 10 kHz, was found to have a target strength at infinite range of + 2 dB, near the side aspect.