Title Stock enhancement in black-spot tuskfish Choerodon schoenleinii
Authers Taku SATO, Yuuki KAWABATA, Koich OKUZAWA, Kimio ASAMI, Masato KOBAYASHI, Hideaki YAMADA, Kouki FUKUOKA, Kenzo YOSEDA, Takayuki TAKEBE, Narisato HIRAI, Yuichi AKITA, Atushi NANAMI , Itaru OHTA, Nobuaki SUZUKI, Masayuki CHIMURA, Yoshimasa AONUMA, Masaya KATOH, Takuro SHIBUNO, and Kazuhisa TERUYA
Keywords Choerodon schoenleinii, optimal release strategy, pre-release conditioning, prerelease learning predator, post-release predation, stock enhancement
Citation Bull. Fish. Res. Agen. No.37, 65-83, 2013
Abstract
Stock enhancement, in which mass hatchery-reared juveniles are released in the wild to help enhancing depleted stocks, is one of the fishery management tools of declining resources. Black-spot tuskfish Choerodon schoenleinii is a commercially high value resource in Okinawa, however, its commercial landings has decreased recently. Thus, we aimed to propose the optimal release strategy to enhance black-spot tuskfish stock through the experimental release trials, field investigations and laboratory experiments. Our study showed 1) bigger juvenile size for release, 2) pre-release conditioning to natural environment and their shelters, and 3) pre-release predator learning treatment will reduce post-release predation mortality by piscivorous fishes. However, these countermeasures against post-release predation need to take large labor and costly if mass release is conducted. Therefore, we further investigated whether release of small juveniles can be alternate way not only for attaining success of enhancement of the stock but also for economic feasibility. Our study showed the release of small juveniles to seaweed beds, acting as shelters and foraging habitat, can be the optimal way to enhance the stock if we can estimate the optimal fish density at release. A comprehensive understanding of the ecological interactions between released juveniles and target ecosystem is important in developing effective release strategy.
URI http://www.fra.affrc.go.jp/bulletin/bull/bull37/37-02.pdf