Acoustic Surveys of Spawning Japanese Sardine, Sardinops melanostictus, in the Waters off Western and Southern Kyushu, Japan

Abstract

Biomass of Japanese sardine Sardinops melanostictus was estimated using a quantitative echo sounder (Furuno, FQ-70; 50kHz) from 1990 to 1994 in the waters off western and southern Kyushu, in southwestern Japan, and the relative estimation error was calculated by geostatistics (1-D transitive theory). Sea surface water temperature and current vectors were measured using an electrical thermometer and ADCP (acoustic doppler current profiler), respectively. The estimated biomass of Japanese sardine using -31.5dB/kg of target strength was over 10 million metric tons in 1990, however, the estimated biomass was continuously decreasing. The estimated biomass was about 100 thousand tons in 1994. The distribution pattern of Japanese sardine was changed with biomass strength. In large biomass phase, Japanese sardine was widely distributed over the survey area, but restricted on the neritic area in small biomass phase.