Variability in mantle length-body weight relationships of the swordtip squid in the East China Sea

Abstract

Mantle length-body weight relationships of the swordtip squid Photololigo edulis in the East China Sea were studied using samples from 1986 to 1995 bottom trawl surveys. Allometry formulae of the body weight (BW in gram) against the mantle length (ML in mm) of this squid were estimated by using linear analysis as follows, which showed clear differences between both sexes and sizes by AIC values; in males less than 13 cm ML, BW=2.7730·10-4·ML2.5961, 13 cm and larger, BW=4.1228·10-3·ML2.0429; in females less than 13 cm ML, BW=2.0434·10-4·ML2.6705, 13 cm and larger, BW=1.2271·10-3·ML2.3002. This squid tended to have a more slender body shape in males, and in larger squids regardless of sex. It is suggested that the difference of development of reproductive organs causes the difference of body shape in sex. Mantle length-body weight relationships of this squid by season were also estimated by dividing each sex into two size groups.