In 2021, the current distribution status of seagrass beds in Kagoshima Bay, Kagoshima, Japan was investigated at 77 sites including four sites located outside the bay. At each site, we measured the seagrass bed area by the naked eye using scuba, snorkeling, and coastal walking and recorded the coverage for quadrats (50 cm long and wide), which were randomly placed inside the seagrass bed. In addition, we measured the water quality including temperature, salinity, and nitrogen levels at the study sites or in the laboratory. The results showed that five species of seagrass were confirmed from the 77 sites, including Zostera marina, Zostera japonica, Halophila nipponica, Halophila major, and Ruppia maritima. Of these species, the first three were found in Kagoshima Bay. However, the total area of seagrass beds in Kagoshima Bay drastically declined to 4.39 ha excluding 2.07 ha from outside of Kagoshima Bay, which was only 11.6% of the area observed in 2006 and 2.4% of the area observed in 1978. This decline is a serious concern for the conservation of seagrass beds in this region, particularly since Z. marina in Kagoshima Bay represents the southern distributional limit of this species in Japan.

　This study examined the effect of photochemical efficiency (ΔF/F_m′) in cultivated sporophytes of Pyropia yezoensis f. narawaensis under the conchospore-release suppression treatment resulting from postponement of seeding date. Two types of treatment were used to preserve sporophytes: Exp#1) Preservation in a dark aquarium tank; Exp#2) Preservation with moistened fabrics, without seawater, sealed in containers. Experiments were conducted under these two treatments for 7 days at 18 and 24℃ in the dark. In Exp#1, ΔF/F_m′ gradually decreased after culturing for more than 3 days. However, at 18℃, the values almost returned to their initial levels within one day after removing the shading. Even after the shading was removed, the values had not fully recovered after culturing for 5 and 7 days at 24℃. In Exp#2, ΔF/F_m′ was well maintained throughout the 7-day culture period at 18℃. In contrast, at 24℃, the values gradually decreased as the culture duration extended; however, after rehydration in seawater with the shading removed, the values almost fully recovered. In commercial cultivation, fishermen typically conduct these treatments for a duration of up to 3 days, suggesting that physiologically, treatments within this 3-day timeframe are likely to be appropriate.

　From June to September 2022, we studied the growth, survival, glycogen content, and habitats of Sinonovacula constricta after releasing seedlings on three mudflats (Higashiyoka, Hama and Nanaura) in Saga Prefecture. On each of the mudflats, the bivalves exhibited growth towards August; however, their density reduced. The glycogen content (mg/g) of the bivalves peaked in July (Higashiyoka 7.4, Hama 5.4, Nanaura 7.3) and showed a declining trend from August onward. This suggests that the energy stored during the sexual maturity period from August to September was insufficient. One possible contributing factor to this phenomenon is the anaerobic conditions in the mud during the summer, which might hinder adequate glycogen storage.

　In recent years, algae cultivation in the Seto Inland Sea has suffered damage due to low nutrient concentrations, and so there is a need to develop a technology for applying fertilizer with less environmental impact. In this study, a technique was developed to efficiently supply nutrients by filling cylinders with small holes (Kagawa-style fertilizer cylinder) with fertilizer and gradually releasing the dissolved fertilizer solution inside the Pyropia thalli growing-nets, where the flow velocity is slower than that outside. The vigor and color of Pyropia thalli were improved by this new method and the quality of the product was well recognized by the market.

　Aquaculture of soft-boned fish may be beneficial if such fish are more palatable than ordinary fish. To verify this, a series of experiments was conducted. Juvenile common carp Cyprinus carpio and juvenile honmoroko Gnathopogon caerulescens were fed either low-phosphorus (P) feed or normal-P feed for 1 month. These two groups of fish were compared based on chemical analysis and sensory evaluation (tasting lightly broiled whole fish). The low-P carp (mean body weight 8.7 g) had lower ash, calcium, and P content in bones and scales (p < 0.01), and higher body fat content and condition factor (p < 0.01) compared with normal-P fish (mean body weight 8.0 g). The low-P carp also had softer bones (p < 0.01) by organoleptic evaluation compared with normal-P carp. In honmoroko, however, no such differences were found between low-P and normal-P fish.