Status of resource enhancement and sustainable aquaculture practices in Japan

Contrary to the rapid increase in the world aquaculture production, fish production in Japan has been decreasing slightly due to the decreasing trend in seafood consumption of Japanese. Aquaculture production is approximately 20% in terms of yield, and 30% in terms of market value, of the country s total fisheries production. In Japan, about 80 species are targeted for release for sea ranching and resource enhancement purposes. The local governments (prefectures) are the main driving force in resource enhancement programs. Chum salmon, Oncorhynchus keta, and scallop Mizuhopecten yessoensisis are examples of successful resource enhancement in Japan. Japanese flounder, Paralichthys olivaceus, and red seabream, Pagrus major, represent intensely released fish species in Japan, and around 10% of the total catch of those species are estimated as released fish. The low price of products and increasing costs of production, such as costs of fuel and fish meal, are the major pressing issues in coastal fisheries and aquaculture in Japan. For aquaculture, the guarantee of food safety, minimization of environmental impact, and management of natural stock populations are highly necessary in order to achieve the sustainability of the industry. For resource enhancement, budget constraint is the major issue, and possible impact on natural stocks caused by released fish should also be considered. The Government of Japan (GOJ) is implementing some measures to rectify unstable business practices of aquaculture and to improve production techniques in aquaculture. For resource enhancement, the GOJ encourages cooperation among local governments (prefectures) for seed production and release of certain targeted species in order to reduce the cost and improve the efficiency of stock enhancement. In Japan, traditionally, the purpose for release was mainly sea ranching, namely harvesting all released animals. Nowadays, actual resource enhancement, i.e. the integrated release program including resource management and development of suitable nursery for released fish, is encouraged by the government. The evaluation and counter measures for the negative impact of stocked fish on genetic diversity of the wild population are also implemented. Recently, marked progress was achieved in seed production technologies of two important tropical fish species, namely coral trout, Plectropomus leopardus, and humphead wrasse, Cheilinus undulatus. These technologies are expected to contribute to the advancement of the aquaculture industry in the South East Asian region

Preliminary result of the relationship between the breathing frequency and dynamic body acceleration

March 5-6, 2009, Bangkok, ThailandIn this study, the relationship between the breathing frequency and the dynamic body acceleration (DBA) of one hatchery-reared loggerhead turtle Carretta carretta was examined using acceleration data loggers. Two acceleration data loggers (M190L-D2GT, W1000-3MPD3GT, Little Leonard, Japan) were attached on the lower-beak and carapace of a hatchery-reared loggerhead turtle, respectively. Breathing was successfully detected from the angle and depth of the beak-attached data logger and DBA, which has been used as an index of activity levels (Wilson et al., 2006), was calculated from the forward acceleration of the carapace-attached logger. There was a positive correlation between the DBA in the previous dive and the breathing frequency; the relationship was exponential. The result suggests that the number of breaths increased exponentially after a more active dive

The SEAFDEC/AQD experience in stock enhancement

The Aquaculture Department (AQD) of the Southeast Asian Fisheries Development Center (SEAFDEC) started stock enhancement activities in 2000 as part of the Coastal Fishery Management Project in Malalison Is., Culasi, Antique, Philippines (SEAFDEC/AQD 1998). This was the same year as the Bangkok Declaration and Strategy for Aquaculture Development (NACA/FAO, 2000), which affirmed the potential of stock enhancement to increase fish supply. Since then, research on seed production, and release and monitoring strategies has been initiated on the abalone (Haliotis asinina), seahorses (Hippocampus barbouri, and H. kuda), mud crabs (Scylla serrata, S. olivacea and S. tranquebarica), top shell (Trochus niloticus), and window-pane oyster (Placuna placenta). Closing the life cycle and mass production of juveniles have been attained for most of these species, but actual releases have been conducted only for abalone and mud crabs. In this review article, we describe the present situation of stock enhancement of abalone, mud crab and seahorse at AQD

Effect of shelter acclimation on the post-release movement and putative predation mortality of hatchery-reared black-spot tuskfish Choerodon schoenleinii, determined by acoustic telemetry

In this study, the effect of shelter acclimation on the post-release movement and putative predation mortality of hatchery-reared black-spot tuskfish Choerodon schoenleinii was examined using acoustic telemetry. We acclimated four 1-year-old fish to shelters in cages before release and compared their movements with six nonacclimated fish. Since it was not possible to compare the behavioral pattern between the former and the latter fish due to the short periods the latter fish were available to be monitored, we also compared their movements with those of large nonacclimated fish that were less likely to be preyed upon. Sixty-seven percent of the nonacclimated fish showed atypical movements before the signals ceased to be detected, a pattern that suggested a predation event had occurred, whereas none of the acclimated and large nonacclimated fish showed the atypical movements. In addition, the probability of detection cessation was about 13 times lower in the acclimated than nonacclimated fish. The signal detection patterns suggest that the acclimated fish utilized night-time shelters from the first night after release, while the large nonacclimated fish started to utilize shelters several days after release. Therefore, it is likely that the shelter acclimation enhanced the shelter utilization by tuskfish, possibly decreasing post-release predation mortality