1Oita Prefecture Eastern Region Bureau, Kunisaki, Oita 873-0504, 2Inland Sea Division, Yamaguchi Prefectural Fisheries Research Center, Yamaguchi 754-0893, 3Buzenkai Laboratory, Fukuoka Fisheries and Marine Technology Research Center, Buzen, Fukuoka 828-0022, 4National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency, Hastukaichi, Hiroshima 739-0452, Japan
Stock size of the mud dab Pleuronectes yokohamae in Suo-Nada of the Seto Inland Sea, which is one of the target species for the stock recovery project, was estimated by a tuning VPA with catch per unit effort data. The Plan of fisheries management of the mud dab was examined based on spawning per recruit (SPR). The stock size decreased from 2,571×104 individuals in 1980 to 1,024×104 individuals in 2003. The recruits decreased from 780×104 individuals in 1980 to 252×104 individuals in 2002. The spawning biomass declined from 1,250 tons in 1980 to 609 tons in 1996, and remained at a low level of 579-688 tons in 1997-2003. The average of percent spawning per recruit (%SPR) over twenty-four years (1980-2003) was 17%. A recent decrease in fishing effort of the small trawl net and gill net fisheries made the %SPR higher than 20% which is its lower limit for sustainable use of spawning stock. A further decrease in the fishing effort or an increase in the age at first capture may enable %SPR to approach 30% which is a desirable level.