抄録
東北海域におけるマダラ資源にVPAを適用して得られた資源量推定値をもとに,トロール調査に基づく面積密度法による資源量推定に必要な漁獲効率を推定した。1歳と2歳の漁獲効率はそれぞれ0.54,0.12と大きな差がみられた。1歳魚については調査範囲が生息域を網羅していることから,漁獲効率はトロール網の前にいた個体の入網率を反映した値であると考えられる。2歳魚以上では,着底トロール調査が困難な岩礁域等にも生息することから,漁獲効率は入網率に加え,網との遭遇率の影響も受けていることが示唆された。
Fishing efficiency is one of the most important parameters to estimate population size using the swept area method based on bottom-trawl surveys. In the present study, the fishing efficiency of the stock of Pacific cod Gadus macrocephalus in the waters off the Pacific coast of northern Honshu, Japan was estimated based on the abundance obtained from virtual population analysis. Fishing efficiencies were estimated to fit the population size obtained from the swept area method to that obtained from virtual population analysis. Fishing efficiency was estimated as 0.54 for 1-year-old and 0.12 for 2-year-old fish, which had a significant difference. This is because, the fishing efficiency of 2-year-old fish was mainly affected by encounter rate to fishing gear caused by the difference of distribution area among the fish of different ages; many of the 2-year-old and over fish distributed on un-trawlable parts, e.g. rough-bottomed reefs.
