Changes in Some Properties of Black Sea Bream Released into the Daiô Bay, Hiroshima

Abstract

In order to evaluate seed quality for release projects, body constituents of artificially-produced black sea bream Acanthopagrus schlegeli were monitored after release. The individually marked fish (42 mm in total length) were released into a Daio Bay of Nino-shima Island, Hiroshima, in August 1993. The hatchery-produced fish which had high lipid reserves lost them abruptly within one month af ter release. Thereafter, the lipid level became lower than that of wild fish at the 100th day. Intestinal length of hatchery-produced fish was shorter than that of wild fish, but extended to the same length to wild fish by living in the sea. Activity of the hepatic enzyme glucose-6-phosphate dehydrogenase (EC 1.1.1.49) involved in lipogenesis was higher in hatchery-produced fish but reached the same level as that in wild fish at one month after release. Activity of hepatic 6-phosphogluconate dehydrogenase (EC 1.1.1.44) remained constant during the experimental period. The changes in the body constituents could be helpful in evaluating fish quality in releasing projects.

Reduction in size-at-age of black sea bream (Acanthopagrus schlegelii) following intensive releases of cultured juveniles in Hiroshima Bay, Japan

“…Subsequently, total harvest increased to >200 tonnes per year and Hiroshima Bay is now the primary fishing ground for this species in Japan, accounting for 10% of total domestic landings. The recovery of the black sea bream population is generally attributed to stock enhancement (Umino et al, 1999;Nakagawa et al, 2000;Blanco Gonzalez et al, 2008a): the cultured juveniles appear to acclimatize rapidly to the natural conditions and grow at the same rate as wild fish within a few months of release (Yamashita et al, 1997;Umino et al, 1999;Nakagawa et al, 2000;Jeong et al, 2007).…”

Managing the Genetic Resources in the Intensive Stock Enhancement Program Carried out on Black Sea Bream in Hiroshima Bay, Japan

“…Once released, stock enhancement programs aim at maximizing fitness performance and minimizing negative genetic or ecological interactions between wild and hatchery fish. Several experiments using non-genetic markers indicated high survival and fast acclimation of black sea bream juveniles released in Hiroshima Bay (Ji et al, 2003;Nakagawa et al, 2000;Umino et al, 1999;Yamashita et al, 1997). However, limitation of food resources related to the stock enhancement program was suggested to explain the reduction on size-at-age recorded on the adults collected in 2000 compared to 1983 .…”

“…They were reared in indoor tanks and released at 3 cm in total length. Initially, released juveniles were identified marking their otoliths with alizarin-complexon and by ventral fin-clipping (Nakagawa et al, 2000;Umino et al, 1999;Yamashita et al, 1997). Using non-genetic markers, it was possible to investigate the acclimation process (Nakagawa et al, 2000;Yamashita et al, 1997), migration (Anonymous, 1987) and optimum size-at-release (Umino et al, 1999).…”

“…Initially, released juveniles were identified marking their otoliths with alizarin-complexon and by ventral fin-clipping (Nakagawa et al, 2000;Umino et al, 1999;Yamashita et al, 1997). Using non-genetic markers, it was possible to investigate the acclimation process (Nakagawa et al, 2000;Yamashita et al, 1997), migration (Anonymous, 1987) and optimum size-at-release (Umino et al, 1999). Later on, the development of microsatellite DNA markers (Jeong et al, 2003(Jeong et al, , 2007 has contributed to address fundamental questions regarding the effects of the releases on the genetic resources of the natural stock.…”

Gut characteristics and assimilation efficiencies in two species of herbivorous damselfishes (Pomacentridae: Stegastes dorsopunicans and S. planifrons)

“…Morphological changes in intestinal or surface area may be short-term, phenotypic responses to the nature and quantity of food resources (Nakagawa et al 1999). For example, hatchery-reared black sea bream, Acanthopagrus schlegeli, have significantly shorter relative intestine lengths than wild fish of the same size (Yamashita et al 1997); once the hatchery-reared fish are released into the wild, their relative intestine length increases until they are indistinguishable from wild fish. Relative intestine lengths in hatchery-raised ayu, Plecoglossus altivelis, are greatest in individuals fed only 60% of the ration of other experimental fish (Nakagawa et al 1999).…”