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Study on artificial seed production of the brackish water bivalve Corbicula japonica in Hokkaido

ISSN: 2185-8012

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  • Title:
    Study on artificial seed production of the brackish water bivalve Corbicula japonica in Hokkaido
  • Author: Sasaki, Yoshitaka
  • Subjects: Bacillariophyceae ; Bivalvia ; Brackish ; Chaetoceros calcitrans ; Corbicula japonica ; Freshwater ; Salmonidae
  • Description: Freshwater Fisheries and Aquaculture produced about 7 thousand tons of fishery resources in 2007 in Hokkaido Island (Japan). Production of the brackish water bivalve, Corbicula japonica accounts for about 15 percent of total production. The production of the brackish water bivalve peaked in the 1980s, and has declined since the 1990s in Hokkaido. The decrease of catch occurred mainly in Teshio River, Lake Panke and Ishikari River. Regulations have been implemented in these areas to restrict the fishing quota and, fishing season. However, the status of bivalves is in danger of depletion because there is no recruitment. Artificial propagation is required in order to produce fishery resources, while continuing resources management of wild production to sustain fisheries. It is necessary to investigate the annual reproductive cycle, artificial insemination conditions, breeding conditions of parents, inducing conditions of sexual maturation, feeding methods of larvae and juveniles and selective breeding programs in order to establish artificial propagation. We investigated the annual reproductive cycle, determined the optimal environmental conditions for artificial propagation and identified the season in which survival of captive-bred larvae was highest in Teshio River and Lake Panke. The soft tissue index (soft tissue weight x 100 / total weight) and the gonad index (gonad weight x 100 / total weight) gradually increased from June to July, and sharply declined in early July. Judging from histological observations of the gonads, spawning occurred in early July. Artificial spawning was most successful at 5 psu and water temperature of 25 degree C. Among spawnings between early July and early August, the captive-bred larvae produced in early July showed the highest survival rate. These results indicate that the survival of captive-bred larvae is dependent on the timing at which artificial spawning is undertaken. It is said to promote efficiency of it because laying eggs is hasty by maturity promotion the artificial seed production. C. japonica collected in the early spawning season were bred in different water temperatures from 12 to 30 degree C for one month; the gonad index of females increased at high water temperature and more spawning eggs were produced. The gonad index of males increased at low water temperature from 12 to 20 degree C. Sperm motility decreased from early August to early September. When C. japonica, which was collected in early June of the maturing season, was bred in different water temperatures and photoperiods for two months, the soft tissue index and the gonad index of males females did not increase. On the other hand, when C. japonica was collected in the mid-July, slightly earlier than the spawning season, and the water temperature was raised gradually to 25 degree C from one to two weeks, more spawned eggs and free-swimming larvae were produced. In addition, in the group that was fed by Chaetoceros calcitrans for two weeks, there was little decrease of the gonad index in comparison with that of no feeding, and then more spawned eggs and free-swimming larvae were produced. These results show that the maturity of C. japonica is promoted by regulating the water temperature from the early spawning season; the breeding water temperature for males and females to coincide for artificial spawning is from 20 to 25 degree C. The parents must be fed to obtain high survival rate of the seeds. It is necessary to identify the kind of food, and to establish the optimal quantity and feeding method for larva and juvenile. C. calcitrans, leaf mold solution or diatom powder were given to free-swimming larvae of C. japonica; when given with C. calcitrans, the rate of juveniles showing high performance was high and all of them reached the stage of settled juveniles earlier than those fed other foods for 22 days. When the larvae of bivalve were reared with a water tank of 100 liters for 54 days, their survival rate was the highest for C. calcitrans, and their average shell lengths was the biggest in those fed on diatom powder.
  • Creation Date: 2011
  • Format: 1-47
  • Language: Japanese
  • Identifier: ISSN: 2185-8012
  • Source: Freely Accessible Japanese Titles
    AgriKnowledge（アグリナレッジ）AGROLib
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