FRA

　Most jack mackerel Trachurus japonicus caught from the Sea of Japan are mainly spawned in the East China Sea and migrate into the Sea of Japan through the Tsushima Strait. This study was conducted to identify this migration route. Surveys were conducted by three research vessels using midwater trawls to determine the distribution of pre-recruit Jack mackerel and its relation to the Tsushima Current from late May to middle of June in 2002. Jack mackerel were caught in 42 of 48 tows （maximum catch : 474, station average : 38.2）. The average fork length at each station ranged 28.3-54.2mm. Based on previously published age-length data, these fish were estimated to have hatched between April and early May in 2002. Jack mackerel were caught mainly in the onshore branch of the Tsushima Current, and few were caught in the offshore branch, suggesting that most pre-recruit jack mackerel were transported into the Sea of Japan by the onshore branch of Tsushima Current.

Harmful bloom-forming algae, Heterosigma akashiwo （Hada） Hada （Raphidophyceae） and Heterocapsa circularisquama Horiguchi （Dinophyceae） cause a mass mortality of cultured fish and bivalves, respectively. In recent years, a double-stranded DNA （dsDNA） virus HaV infectious to H. akashiwo, and a dsDNA virus HcV and a single-stranded RNA （ssRNA） virus HcRNAV, both infectious to H. circularisquama were isolated from natural seawaters in Japan. These viruses have some important characteristics suitable as microbiological algicidal agents. However, from the viewpoint of risk management, evaluation of their effects on various organisms is essential to assess the possibility of their use for eliminating the harmful algal blooms. In the present study, we have evaluated effects of the viruses on marine organisms （bivalves, zooplankton, seaweeds and fishes） and mammals （a mouse）, and revealed that there was no significant acute toxicity against the tested organisms through the experiments. These results suggest that the algal viruses are safe for other organisms.

　Marine bio-resources have been utilized mostly by catch by mankind. In future, however, the marine bio-resources are expected to be highly utilized by developing novel fish culture skills and food processing techniques. Fermentation skills are greatly contributing to food producing and processing industries today. However, most fermented products are terrestrial origin and marine origin products are quite limited. Especially, a skill to ferment algal materials （plant materials of marine origin） has never been developed in the field of fisheries industry.
　The author firstly developed a skill to perform a lactic acid fermentation of seaweed. The following is a summary of the results obtained by the present study.

1） Lactobacillus brevis strain B5201, Debaryomyces hansenii var. hansenii strain Y5201, and Candida zeylanoides-related strain strain Y5206 were isolated as predominant microorganisms in a fermented material of Ulva spp. fronds.
2） A skill to perform lactic acid fermentation of seaweed was developed by a combinational use of cellulase and starter microorganisms that are composed of the above three isolates. Production of single cell products at high efficiency from algal frond tissue was observed during the fermentation of Undaria pinnatifida.
3） PCR-methods to estimate the predominance of the microorganisms added as a starter to cultures for seaweed fermentation were developed. L. brevis strain B5201 could be detected by use of a species-specific primer set targeted for 16S rRNA gene. Yeast strains Y5201 and Y5206 could be detected by use of an arbitrary synthesized primer OPA-3 and PCR-RAPD method.
4） Single use of lactic acid bacteria as a starter was effective for preventing the growth of contaminant microorganisms, while single use of yeast was not effective. Lactic acid bacteria having homo-type fermentation such as Lactobacillus plantarum and Lactobacillus casei showed high predominating ability as well as L. brevis in fermentation cultures of U. pinnatifida.
5） Dietary effect of fermented products of U. pinnatifida （marine silage） was demonstrated by rearing trials with young pearl oyster Pinctada fucata martensii.
6） Reduction of triacylglycerol concentration in serum and liver was observed for rats fed the diet supplemented the fermented Undaria product at 10 ％ level for three weeks, suggesting possible utilizations of fermented materials of seaweed as new food items.