Previous studies have reported that the use of light is effective for fishing, and specific wavelength light and aquarium colors are effe ctive for control maturity, growth and survival of fish. Thus, the use of light in fishing and aquaculture has a long history. In the current study, we reviewed previous findings regarding the relationship between fish visual function, the ocean light environment, and responses of fish to light. We examined the effects and problems associat ed with the impacts of artificial light on fish behavior. The findings highlight the importance of understanding the ecology of adult fish during development from larvae, as well as visual func tion, behavioral responses to light, and physiological responses of fish at each developmental stage. Clarifying these issues is necessary for elucidating the most effective light conditions for fishery, seed production and aquaculture.
To examine seawater exchange in Matsushima Bay, we analyzed monthly tempera ture and salinity data, obtained by the Miyagi Prefecture, and temperature monitoring data provided by the Sena and Varns Corporation. The difference in surface temperature, between water inside and outside of the bay, is larger in early summer and late summer, and decreases in mid summer, indicating two peaks in the warming season. A temperature fluctuation with a several-day period was strongly correlated to the northwest-southeast wind component, which dominated from early summer to fall. The correlation indicates that the temperature decrease was induced about 2 days after southeastward wind events. In order to clarify these mechanisms, we employed the Regional Ocean Modeling system (ROMS) using observed atmospheric data. After reproducing the temperature variation from spring to fall. we found that over a several-day period, wind induced seawater exchange and variation in the temperature difference between water inside and outside of Matsushima Bay. Monitoring data and model results confirmed that an internal tide was generated in the bay during the formation of a thermocline that occurred after the southeastward wind. These results indicate that wind-induced seawater exchange occurs in Matsushima Bay.
Sablefish otoliths (sagittae) collected from four areas (Northern California, Gulf of Alaska, Bering Sea, and Aleutian Islands) in 1984 were used to determine age by the section otolith aging method, and to measure otolith radius and thickness. The relationship between otolith ratio (radius/ thickness) and age was linear in the four areas. There was no statistical difference in the comparison of the age-otolith ratio relationship between the Gulf of Alaska, Bering Sea and Aleutian area; however, that of Northern California was found to be significantly different from the other three. These results are in keeping with the two-population hypothesis of previous tagging studies. Thus, sablefish otolith measurements might be a sensitive characteristic for discerning sablefish population structures. Further studies of otolith morphometric analysis including shape might provide an even clearer picture of sablefish populations.