SEX COMPOSITION AND SEXUAL MATURITY OF SEPIA-ESCULENTA CAPTURED IN CUTTLEFISH BASKET TRAPS

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 matu rity. Females were caught in significantly greater numbers (58%) than males, and the sex ratio (female/male) tended to increase between Febr uary and May. The observed frequency of traps with only male or only f emale catch did not follow Poisson's distribution. From one to a maxim um of four females appeared in each of 292 traps, and 1-5 males in eac h of 114 traps. All males and the majority of the females were sexuall y mature from December to June, except for two females captured in Dec ember 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 re sults indicate that spawning and mating behavior are not the only fact ors governing the entry of cuttlefish into traps, but that there are p robably some other factors which are still unknown.