Fishery Performance Indicators (FPI) is a framework for comprehensive fishery management assessment from three aspects: ecology, economics, and community. This paper evaluates the management of the Pacific offshore Danish seine fishery in Hokkaido, Japan, using the FPI and compares it to assessments of 149 fisheries in Japan and overseas. The ecology score was 4.25, ranking 27th, and the community score was 4.31, ranking a very high 18th. The economics score was 3.41, ranking 71st, which was not very high. This result may reflect the characteristics of Japanese-style fishery management, which emphasizes community rather than economic aspects of fisheries.

　The total allowable catch (TAC) management system was newly introduced for the disk abalone diving fishery in the Yoro district, Miyazu, Kyoto prefecture, Japan, in 2021. As a result, aggressive competition for catching was triggered because the derby fishery was adopted, so the management system was abolished in the same year. Subsequently, the individual quota (IQ) system was newly introduced instead in 2023. The impacts of the TAC and IQ management system on the catchability were assessed by the DeLury method based on catch statistics for the period 2019–2023, and the calculation was by the maximum likelihood method in which two approaches were compared: with and without taking the catchability differences by fishermen into account. The former approach was adopted as a result of the comparison of AIC, and the catchability coefficients were significantly elevated in the years 2021 and 2023 compared with other years. As the coefficients were notably high in 2021, the occurrence of aggressive competition on catch was corroborated. The introduction of the TAC system with the derby fishery could trigger the race to fish also in small-scale coastal fisheries, such as the abalone diving fishery.

　We investigated the strain identification between hatchery-reared and landlocked ayu Plecoglossus altivelis altivelis using meristic character (number of scales above the lateral line based on the dorsal fin ray) and otolith Sr:Ca ratios in the upper reaches of Kagami Dam Lake in the Kagami River. The percentages of landlocked and hatchery ayu in angling (tomozuri) caught fish in May–September in 2017 were 17–92％ and 8–83％, respectively. Using microsatellite DNA markers, we examined the reproduction of landlocked and hatchery ayu in Kagami Dam Lake. The genetic origin of parent and upstream migrated populations in the landlocked form in Kagami Dam Lake was identified as hybrid fish between amphidromous and Lake Biwa strains using assignment tests. Moreover, among the spawning in November and December, 23–27％ of individuals were identified as amphidromous strain, suggesting that hatchery-reared ayu contributed to the reproduction. These results indicated the contribution of hatchery-reared ayu to the reproduction and enhancement of resources in Kagami Dam Lake and its upper reaches. However, most individuals within the upstream migrated population were identified as hybrid fish. This indicates that most of the ayu in Kagami Dam Lake are hybrid fish, and their reproduction contributes to the persistence of the population.

　Aphanothece sacrum (Suizenji-Nori in Japanese), an edible fresh water unicellular cyanobacterium, has been cultured since the 1750s using oligotrophic running water in Kyushu Island, Japan. An exopolysaccharide (EPS) of A. sacrum (Sacran^®) is currently attracting attention because of its physico-chemical properties such as high water retaining capacity and heavy metal ion adsorption. However, the production of A. sacrum in traditional aquafarms, which peaked in the 1990s, has decreased to less than 5％ due to water eutrophication and/or groundwater depletion. We developed a simple medium-size indoor culture system using a unialgal strain of A. sacrum. Cells were inoculated into polyethylene bags filled with culture medium, then incubated at 22–24°C under the illumination of cold-cathode lamps (13–15 µmol photons m⁻² s⁻¹, 12 h:12 h light and dark cycles) for 4 months. The yield of A. sacrum was estimated to be about 3.5 kg (net weight) m⁻² year⁻¹. The contents of EPS of A. sacrum were > 50％ on a dry-weight basis.

　Large amounts of appropriate food are required to promote the maturation of the pen shell broodstock. Due to the costs involved, broodstock conditioning is done through a combination of sea rearing and short-term tank rearing. Because the optimal timing for tank rearing is not well understood, we examined the maturation, nutritional status, and spawning of broodstock reared in tanks for one month starting in either April (FE1) or May (FE2). The broodstock was fed with Chaetoceros neogracile (100 million cells/g soft body weight/day), and the water temperature in the tank was maintained at 22°C. In the FE1 group, the ovaries regressed from the early or late developing stages to the early regressive stage. In the FE2 group, the ovaries progressed from the late developing stage to the ripe stage. The testes in both groups progressed from the early or late developing stages to the ripe stage. Spawning behavior was observed only in the FE2 group. These results suggest that under the rearing conditions used in this study, early initiation of tank rearing set back ovarian development. The late stage of ovary development can be used as an indicator of the appropriate time to begin tank rearing.

　Karasumi, a salted-dried mullet (Mugil cephalus) roe, is consumed worldwide. Anjo is widely utilized to increase the drying rate of Karasumi during the manufacturing process. However, the detailed influence of different Anjo processes (pressing, wrapping, and pressing-wrapping) on the water behavior and quality of Karasumi during drying remains unclear, and thus, their effects were investigated. Moisture content and ¹H T₂-enhanced images obtained from magnetic resonance imaging (MRI) analysis clarified that the pressing Anjo method was the most effective in promoting the drying of Karasumi. An increase in Young’s modulus and acceleration of browning were observed in the pressed sample with the progress of drying. Furthermore, the pressed sample did not exhibit the surface irregularities and internal cracking observed in the control sample. Therefore, the pressing Anjo process during the production of Karasumi is effective not only in accelerating drying, but also in improving its visual properties, such as shape and prevention of cracking.

　The purpose of this study was to verify the effect of slaughtering method of fish, including spinal cord destruction, aiming for the long-term retention of freshness after slaughter, and to examine consumer evaluations. White trevally Pseudocaranx dentex was used for this study. To verify the freshness retention effect of spinal cord destruction, freshness was measured for approximately 10 days using a handy device (Fish Analyzer^TM Pro) for white trevally slaughtered by different methods. To examine consumer evaluations, tasting experiments were conducted at Tsukiji, Tokyo, where various small-scale fish retailers and restaurants are located. Japanese and non-Japanese volunteers were invited on a first-come first-served basis, to taste white trevally sashimi prepared by different slaughtering methods. The results showed that spinal cord destruction was more effective than simple spinal cord cutting for retaining freshness in terms of measurements by the device. However, the difference in consumer evaluations between the two slaughtering methods was not significant. Therefore, the value of spinal cord destruction is considered to be mainly for extending the life of the product.