Recruitment Patterns of Cultured Juvenile Pacific Threadfin, Polydactylus Sexfilis (Polynemidae), Released Along Sandy Marine Shores in Hawaii
Release-recapture studies were conducted with Pacific threadfin, Polydactylus sexfilis , the species given highest priority for stock-enhancement research in Hawaii. Their purpose was to evaluate recruitment potential, dispersal, growth, and differential recapture rates of cultured fingerlings released into shoreline juvenile nursery habitats along the windward (eastern) coast of Oahu, Hawaii. We varied fish size at release, release site, and the seasonal timing of releases using a balanced, randomized-block experimental design. After releases of 20,000 tagged Pacific threadfin in 1993 and about 81,000 in 1994, we recaptured 1705 cultured juveniles in net collections made over a 17-mo period. Presence of cultured fish in net samples depended strongly on the interactive effects of release variables. Size at release had an important effect on recapture rates at all release sites, but this effect varied seasonally. At one of the release sites, larger fish apparently had better survival after winter releases and smaller fish had better survival after summer and fall releases. Release site affected dispersal patterns, recruitment, and recapture rates. The percentage of cultured fish in samples of Pacific threadfin taken 8 mo after release varied from 0% to 64%. Cultured fish showed strong site fidelity at some sites, weak at others. What we considered “pilot”-scale releases clearly were large enough to approach swamping wild recruitment at Kahana Bay. A key question from this study is how many cultured juvenile Pacific threadfin the Kahana Bay site can support without displacement of wild individuals.
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Document Type: Research Article
Publication date: 1998-03-01
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