Evaluation of the stocking efficiency of giant cuttlefish Sepia latimanus hatchlings through marking experiments

To evaluate the stocking effectiveness of giant cuttlefish hatchlings, 25-62 thousand individuals were annually marked on the cuttlebones with Alizarin red S and stocked into Urasoko and Kabira Bays of Ishigaki Island, Okinawa, southernmost Japan from 2001 to 2003. The giant cuttlefish caught by small set-nets in the bays and the cuttlebones collected from a fish market and five coastal beaches were examined to detect the marked cuttlebones and to measure the growth of released individuals. Released cuttlefish were caught in the bays where they were released from autumn in the release year to the spring two years later, and the proportion of released cuttlefish in catches ranged from 4.5 to 18.0%. The cuttlebones with marks were mainly collected on the beaches around the release sites. Based on these results, recapture rates and the yield per released individual were estimated at 0.02-0.08% and 0.24-1.28 g, respectively.