Spawning biomass estimates of chub mackerel Scomber japonicus of Pacific subpopulation off central Japan by a daily egg production method

Spawning biomass of chub mackerel Scomber japonicus was estimated for the P acific subpopulation off central Japan in 1996 by a daily egg production me thod. The 451 samples of the adult mackerel used for estimating the biologi cal parameters were collected for April to June in 1996 from the research t akes and commercial catch in the waters around Izu-Islands. Spawning freque ncies were 9%, 47% 47% and 47% for the respective months. Batch fecundities for the 3 months were 31,097, 27,600 and 21,500 eggs/female. Spawning biom ass was estimated to be 35,000 t for June when the spawning activity was hi ghest among the 3 months.