Distributional changes of roughscale sole (Clidoderma asperrimum) off the Pacific coast of northern Honshu, Japan

Abstract

Total catch of roughscale sole Clidoderma asperrimum off the Pacific coast of northern Honshu, Japan (Tohoku area, 35°00’-41°30’N) decreased from 6,329 tons in 1978 to 108 tons in 1998. In this study, the monthly distributional changes of roughscale sole were examined using catch per unit effort (CPUE) data off Miyagi, Fukushima and Ibaraki Prefectures (southern Tohoku, 35°00’–39°00’N) in 1972–2005. Main fishing grounds were formed off Miyagi and Ibaraki in the 1970s/1980s, but the CPUE of this species decreased in all areas in the 1990s. In 2003–2005, the CPUE was low off Miyagi and Fukushima, while the CPUE off Ibaraki showed an increase during February–April. Histological observations of gonads indicated that all individuals (n=22) caught off Ibaraki in February 2007 were spawning fish. These results suggest that the spawning population decreased from the 1970s to the 1990s/2000s, and adult fish migrate to spawning grounds only off Ibaraki in recent years. Fishing control in the spawning grounds should be executed for the resource recovery of the population.