科研之友
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摘要
To understand the age-based life cycle traits of the broadclub cuttlefish Sepia latimanus, we obtained biological information about the species through release-recapture experiments, where 166 345 hatchlings with markings in their cuttlebones were released into their natural habitat of Ishigaki Island, southern Japan, and 96 adult cuttlefish were recaptured over 2 successive years. Age groups were determined based on 3 indices: the number of lamellae in the cuttlebone, dorsal mantle length (DML), and the collection date of wild cuttlefish. The length-frequency data of DML, reconstructed from 4340 cuttlebones collected from either a fish market or coastal beaches, were analysed over a period of 3 yr. The cuttlefish consisted of 2 age groups (0 yr and 1 yr), and each group is thought to die after maturation at the end of the spawning season, indicating that they are different breeding groups. The ratio of 1 yr cuttlefish to total cuttlefish was highest at the beginning of the breeding season (November) and gradually de creased throughout the breeding season. Abundance, maturation, and mating conditions of each breeding group and the estimated hatching season of cuttlefish in the wild suggest that the 0 yr and 1 yr groups contribute equally to production of offspring early in the hatching period, while the contribution of 0 yr cuttlefish is larger later in the hatching period. Offspring hatched later may return as recruits to breed as 1 yr cuttlefish the following year. Our analysis highlighted that the population of broadclub cuttlefish is composed of 2 breeding groups with alternative short and long life spans. This is the first study in which the life cycle traits of a Sepia species have been successfully clarified with release-recapture experiments.
- 出版日期2012
