Possible Relationship between Oceanographic Conditions and Long-Range Target Detection by a False Killer Whale

• Main Authors: Turl, Charles W., Thomas, Jeanette A.
• Other Authors: NAVAL COMMAND CONTROL AND OCEAN SURVEILLANCE CENTER RDT AND E DIV SAN DIEGO CA
• Format: Text
• Language: English
• Published: 1993
• Subjects: Biology; Biological Oceanography; Acoustic Detection and Detectors; *TARGET DETECTION; *AUDITORY PERCEPTION; TEST AND EVALUATION; VELOCITY; DIAMETERS; MEASUREMENT; RATIOS; TEMPERATURE; MODELS; CONDUCTIVITY; WATER; ANALYSIS OF VARIANCE; ACOUSTIC DETECTION; STAINLESS STEEL; SPHERES; STEEL; VARIABLES; SURFACES; DOLPHINS(MAMMALS); WHALES; AQUATIC ANIMALS; OCEANOGRAPHERS; TARGET STRENGTH; HEARING; HAWAII; SONAR; SALINITY; BANDWIDTH; DISCRIMINATION; OCEANOGRAPHIC DATA; PROFILES; LONG RANGE(DISTANCE); SOUND TRANSMISSION; SOUND; MARINE BIOLOGY; NOISE; *KILLER WHALES; PSEUDORCA CRASSIDENS; MARINE BIOSYSTEMS; PE62435N; WUDN688674; Killer Whale
• Online Access: http://www.dtic.mil/docs/citations/ADA265165; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA265165

A false killer whale (Pseudorca crassidens) target detection experiment was conducted on the Skyhook II biosonar target range in Kaneohe Bay, Hawaii. The target was a 7.62-cm diameter stainless-steel sphere. The target distance varied from 80 to 120 m. Normally a morning (0800) and afternoon (1300) test session was conducted each day. The maximum target detection threshold at 50%. correct detection for all test data was estimated to be 117 m. There was, however, a significant difference in the whale's performance between the morning and afternoon test sessions. At target distance greater than 95 m the whale's performance was 52% correct detection during the morning and 91% correct detection during the afternoon test session. We took conductivity and salinity measurements by depth at distances of 0, 50, 100, and 200 m along the range. Sound velocity profiles for each cast were calculated. In the morning, the surface (< 1 m) water temperature and salinity were more variable among the casts, resulting in different sound velocity profiles along the range. Although in some cases the differences were small, their cumulative effects along the range seemed to lower the whale's performance. In contrast, during the afternoon sessions, water temperature, conductivity, and the resulting sound velocity profiles for the four casts along the range were more similar from the surface to the bottom which seemed to be related to the whale's higher detection performance.