Sex Composition and Sexual Maturity of Sepia esculenta Captured in Cuttlefish Basket Traps

Abstract

To clarify the catching mechanism of cuttlefish basket traps for Sepia esculenta, the catches of 1,373 cuttlefish basket traps were analyzed for sex composition, and 917 cuttlefish were assessed for sexual maturity. Females were caught in significantly greater numbers (58%) than males, and the sex ratio (female/male) tended to increase between February and May. The observed frequency of traps with only male or only female catch did not follow Poisson’s distribution. From one to a maximum of four females appeared in each of 292 traps, and 1–5 males in each of 114 traps. All males and the majority of the females were sexually mature from December to June, except for two females captured in December and January. Most but not all females carried spermatophores in the buccal area. Cuttlefish preferred to lay eggs at the front side of branches placed outside the traps rather than on the inside. These results indicate that spawning and mating behavior are not the only factors governing the entry of cuttlefish into traps, but that there are probably some other factors which are still unknown. © 1993, The Japanese Society of Fisheries Science. All rights reserved.