Contribution of artificially produced fry of red tilefish Branchiostegus japonicus to commercial landings in coastal waters of the Shimane Peninsula

Abstract

The contribution of hatchery-reared red tilefish released into the coastal waters of the Shimane Peninsula was assessed. Monthly surveys were conducted at Koizu fishing port from 2012 to 2019 to confirm the labeled red tilefish released into the coastal waters of the Shimane Peninsula. Labeled fishes were captured within 45 km of the release point, with 97% captured within 20 km of the release point. The number of labeled fish found was 123, 80 females and 43 males, with an annual bycatch rate of 0.12-1.01%. The estimated number of fish recaptured was 1,105 females and 681 males, for a total of 1,786 fish. The standardized accumulative recapture rate, calculated from the age composition of the fish recaptured and the number of fish released by year, was capped at 4.874% after age 9. The expected price of fish releases was 83.7 yen per fish as a direct effect and the ratio to selling price per seedling was 0.78. The mechanism of reproduction of red tilefish in this area will be an essential theme in the calculation of indirect effects in the future.