Hyperoglyphe japonica and Pagrus major, which are commercially important species for coastal fisheries, are mainly caught by small vessels with pole and line fishing in the waters of the Iki Islands, Nagasaki, Japan. Fishing is done at one or more fishing locations around artificial and natural reef areas during the day. The effect of artificial reefs on standardized CPUE (sCPUE) of H. japonica and P. major was investigated using fishery-dependent data by the delta log-normal approach as an indicator of resource density. For H. japonica, sCPUE increases with the operation time rate on the artificial reef (A-time rate) and total operation time (T-time) of each cruise. For P. major, regardless of whether the fishing location is around the artificial or natural reef area, sCPUE increases with T-time of each cruise. These results indicate that the artificial reef is more effective for increasing H. japonica resource density, and is equally effective for increasing P. major resource density.

　The suitability of the chub mackerel Scomber japonicus for processing depends on its lipid content. Therefore, there is a need for prompt information on fish lipid content on-site at fish markets. Several studies have shown that seasonal variations in fish lipid content are related to gonadal development. In addition, it is known that gonadal development in chub mackerels is affected by stocks. In this study, we examined the seasonal variation of meat lipid content with body size of chub mackerel landed at the port of Choshi between 2007 and 2017. Furthermore, the relationship between lipid content and gonad index was examined. Lipid content was high in the autumn and winter. As the stocks increased, the rise in lipid content appeared earlier. Moreover, lipid content increased with fish size because chub mackerels require lipid as an energy source for spawning. Furthermore, lipid may be required as an energy source for gonadal development. It took seven or eight months for the gonad to develop after the lipid content in chub mackerels increased.

　We examined the method of analysis and quantitation of balenine (Bal) previously reported. In this method, Bal in muscle extract was hydrolyzed to 3-methylhistidine (3-Mehis) and β-alanine in 6 M hydrochloric acid heated at 110℃ for 24 hours, analyzed and quantitated 3-Mehis by automatic amino acid analyzer. And it was found that 3-Mehis content was equal to Bal content before hydrolysis. However, in this study, the minimum variation of 3-Mehis content was achieved at 110℃ for 3 hours by six repetitions of hydrolysis and quantitation of 3-Mehis derived from Bal. In addition, a high linear correlation between 3-Mehis content after hydrolysis and Bal content before hydrolysis was observed at the Bal standard solution concentrations of 0.05 to 10 μmol/mL. The ratio of 3-Mehis content after hydrolysis to Bal content before hydrolysis was not equal but 89%. Based on these considerations, the Bal content of opah Lampris guttatus muscle extract was quantitated and a remarkably high Bal content was found. The Bal content of opah was much higher than that of some species of baleen whales, such as mink whale Balaenoptera acutorostrata, Sei whale B. borealis and Bryde's whale B. brydei.

　Questionnaire surveys of recreational anglers and fishermen fishing for Ayu were conducted around the Okitsu River, Shizuoka Prefecture, from 2010 to 2012, and the recreational value of Ayu fishing was evaluated using the zone travel cost method (ZTCM). The number of recreational anglers and fishermen totaled 65,000-78,000 each year, and approximately 10% of these were recreational anglers from the Kanto area who drove a car using toll roads. The recreational value amounted to 479 million yen and 478 million yen, respectively, and the cost benefit ratio (B/C) was 9.2 and 8.9, respectively, in 2011 and 2012. In addition, the economic effect represented by the fishing charges income benefit ratio (B/I) was 9.2 and 9.1, respectively, in 2011 and 2012. In other words, Ayu fishing results in high recreational value as well as highly efficient stock enhancement.