Long term variability of red sea bream Pagrus major stock in waters around Yamaguchi Prefecture coast off the Sea of Japan by analysis of the fisheries statistics
Imai, C.; Kobayashi, T.
Journal of National Fisheries University 48(3): 221-232
2000
Document Number: 357719
The long term yearly variability for a stock of red sea bream Pagrus major in waters around the Yamaguchi Prefecture coast off the Sea of Japan was analyzed using fisheries statistics. The catch per unit effort (CPUE) was calculated by the statistics of annual catch/day of fishing from 1975 through 1997. Stock assessment was made for the three subdivided waters of Abu-Hagi, Otsu-Nagato, and Houkan. Both the offshore large scale fisheries of western trawl and eastern trawl caught red sea bream. Fishing efforts by the two large trawl fisheries decreased through the periods due to retirements, while western trawl fishery fleets based in the area have disappeared since 1992. The CPUE for eastern trawlers markedly increased in the late 1990s probably due to stock rehabilitation caused by decreasing fishing effort. For coastal fisheries, small trawls No.1 and No.2, gillnet, hook and line, longline, as well as boatseine were the major fishing methods for red sea bream. The overall catch made by a majority of coastal fisheries decreased in the 1980s and slightly increased in the 1990s. Fishing efforts also decreased through this period. The CPUE decreased in the 1980s but were either maintained or in some cases increased in the 1990s. In the Abu-Hagi and Otsu-Nagato areas, red sea bream stock maintained medium levels and showed low variability. The CPUE for the gillnet fishery markedly increased in the 1990s especially in Otsu-Nagato, but did not increase for hook and line and for longline fisheries. The Houkan coast proved to be an important nursery area for sea bream recruits because CPUE was at very high levels for small trawl No.2 and boatseine fisheries, both of which caught many young sea breams. The CPUE of the boatseine fishery in Shimonoseki was marked over a five-year cycle, showing the peak height and the amplitudes progressively decreasing through the late 1980s. Rehabilitation did not occur in the 1990s.