Forecasting the stock size of the autumn cohort of Japanese common squid (Todarodes pacificus) based on the abundance of trawl-caught juveniles

Hideaki Kidokoro, Takafumi Shikata, Shinsuke Kitagawa


The distribution of juveniles of Japanese common squid (Todarodes pacificus) autumn cohort and its relation to oceanographic conditions were analyzed to see if they can be used to accurately forecast the stock size. Research cruises was conducted using a total of 5 research vessels during 2001-2010 in April in the southern Sea of Japan. Juveniles were caught in 267 of 331 tows of a trawl net at approximately 0-10 m depth, and the numbers caught in each tow ranged from 0 to 1087. Samples were divided into the autumn and winter cohorts based on the dorsal mantle length (DML). The autumn cohort was abundant (40 inds / tow) where the sea surface temperature ranged from 10 to 11 °C and less abundant in warmer water. This cohort was more abundant in offshore areas, while the winter cohort was more abundant near shore. The mean catch of the autumn cohort was used as an index of the annual abundance of juveniles. This index and the stock size were significantly correlated. These results suggest that the stock size of the T. pacificus autumn cohort can be forecasted before the fishing season based on the abundance of juveniles, but this relationship is highly uncertain due to observational errors

Palabras clave

Ommastrephidae; predicting stock size; stock management

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