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 (sa) was higher in winter and spring between 2008 and 2009; in the other years it was highest in autumn. The average sa was significantly influenced by depth, temperature, salinity, and turbidity in univariate analyses (p<0.05). However, in linear regression analyses, the average sa significantly increased only with increases in temperature and salinity, whereas the effects of depth and turbidity were not statistically significant.