Spatial and Temporal Distribution of Hairtail (Trichiurus japonicus) in the Bungo Channel, Japan

抄録

To ensure sustainable utilization of the hairtail (Trichiurus japonicus) fishery resources in the coastal and offshore waters of Japan, 15 acoustic surveys were conducted from 2007 to 2013 using a 38 kHz split-beam echo sounder. The hairtail was mainly distributed depth between 80 and 280 m in winter (particularly between 80–120 m), 60–280 m in depth (particularly between 120–160 m) in autumn, and 70–260 m in depth (particularly between 70–140 m) in summer. The average area backscattering coefficient (s_a) was higher in winter and spring between 2008 and 2009; in the other years it was highest in autumn. The average s_a was significantly influenced by depth, temperature, salinity, and turbidity in univariate analyses (p<0.05). However, in linear regression analyses, the average s_a significantly increased only with increases in temperature and salinity, whereas the effects of depth and turbidity were not statistically significant.