Controlling the catch of Pacific bluefin tuna in set nets is an important issue in stock management of the species in order to comply with quotas under international regulations. Bluefin tuna, once inside set net gear, tend to escape naturally due to the structure of set net gear before landing. Investigating the shape of the set net depending on oceanographic conditions, which are relevant for natural escape, may yield clues for controlling the catch. We therefore studied the relationship between fishing conditions and escape behavior of Pacific bluefin tuna by a tagging experiment. The test results were analyzed by a generalized linear model and the best model was selected by Akaike’s information criterion. The explanatory variables were body length of Pacific bluefin tuna, tidal current velocity, bottom of the minimum bag net depth, and elapsed time. The results showed that escape of Pacific bluefin tuna was affected by minimum bag net depth and tidal current speed, because the tidal current raised the bag net bottom and reduced the swimming space for the tuna. These results may be useful for future resource management of Pacific bluefin tuna in set nets.

　Frozen tuna products used as raw ingredients such as sashimi or sushi are typically stored at ultra-low (below −55°C) temperatures in multiple places (i.e. on vessels and on land) in the supply chain. This process uses large amounts of fossil fuels and emits large amounts of CO₂. Raising the temperature of storage sites would reduce not only energy consumption but also CO₂ emissions. However, no quantitative evaluation of CO₂ emissions has been reported when the storage temperature of tuna products is raised. Furthermore, introduction of the measure to reduce environmental impact has not been discussed. We calculated the CO₂ emissions of a fish-hold on a vessel and a cold storage on land and examined the reduction effect by changing the storage temperature for application of life cycle assessment (LCA). We estimated that raising the frozen storage temperature from ultra-low temperature to −45°C reduced CO₂ emissions by 0.60 ton [t-CO₂/t] per ton of fish products. In this paper, we discuss the achievement of both reduction of CO₂ emissions and energy saving in a tuna longline fishery and related industries.

　Based on catch information of large-sized torafugu Takifugu rubripes during the spawning season in Tokyo Bay and reports of the collection of natural juvenile torafugu in the inner part of Tokyo Bay, it was assumed that adult torafugu migrate to the mouth of Tokyo Bay and spawn. As part of a study to examine the spawning migration of torafugu in Tokyo Bay, we analyzed catch records from recreational fishing boats to determine the size characteristics during the spawning season and attempted to sample the demersal eggs to identify spawning grounds. Adult torafugu were caught from mid-March to mid-April in the mouth of Tokyo Bay. In this period, the number of torafugu constituted about 80％ of the total catch for the survey period from March 18 to June 2, 2018. DNA analysis of the sampled eggs revealed that 18 of them were identified as torafugu eggs. This study has identified the mouth of Tokyo Bay as a spawning area for torafugu, which is the second such report on the Pacific side of Japan.

　Before the recent SDGs movement, we have long promoted the advanced use of unused parts of the Akoya pearl oyster (Pinctada fucata) as a cosmetic ingredient, with the goal of sustainable pearl farming. In this study, we focused on the byssus and investigated the potential use of its hydrolysate (PBH) as a cosmetic ingredient. PBH significantly increased the gene and protein expression levels of Endo180, an important factor in collagen production that prevents wrinkle formation, in normal human dermal fibroblast (NHDF) cells. Furthermore, the reduction of Endo180 gene expression in artificially produced senescent NHDF cells was significantly reversed by adding PBH. PBH also increased the uptake of fragmented collagens into NHDF cells, reversing the decreased uptake of these fragmented collagens in the senescent NHDF cells. These results suggest that PBH can suppress the functional decline of senescent cells, and the wrinkle formation associated with the decreased expression levels of Endo180 in these cells, revealing PBH as a promising cosmetic ingredient.

　Ascidian Halocynthia roretzi is a very important aquacultured species on the coast of Miyagi prefecture. In Miyagi prefecture, the harvest season of this species is from late spring to early summer, which is also the season when Alexandrium species as the causative plankton of paralytic shellfish poisoning (PSP) have been observed in the coastal waters. There have been reports on the detection and tissue distribution of paralytic shellfish toxins (PSTs) in H. roretzi, but there are few reports on such tissue distribution throughout the PSP season and on the metabolism of PSTs. In this study, we detected PSTs from H. roretzi throughout the PSP season. The results indicated that most of the PST was localized in the hepatopancreas of H. roretzi throughout the PSP season and there is a possibility that the PST amounts of individuals could be reduced to about 10％ by removing the hepatopancreas of the contaminated H. roretzi.

　This study examined the effects and challenges of the Individual Quota (IQ) management system, which was experimentally introduced for Japanese horse mackerel and chub/blue mackerel in the large- and medium-scale purse seine fishery operating in the Sea of Japan and East China Sea, based on interviews with stakeholders. The interview results revealed that while IQ management was recognized to have advantages, such as enabling fishing strategies that consider the entire season, there were operational challenges. These challenges included: difficulty in realizing the full benefits of IQ due to catch landing restrictions caused by peak fishing seasons and insufficient onshore facility capacity, and the problem of underutilization of quotas caused by multiple species quota allocations. Additionally, the importance of quota transfers was emphasized, suggesting the need for a mechanism to allow quota transfers even within the IQ management system.

Erratum to "The effects of skip and later molters of adolescent male snow crabs Chionoecetes opilio on the biomass of adult males in the Sea of Japan off Kyoto Prefecture"

Nippon Suisan Gakkaishi 2025; 91: 189–199. https://doi.org/10.2331/suisan.24-00014

Wrong : 　　191, Fig. 2

　　　　"110–29 mm", Carapace width of Instar group B

Right : 　　191, Fig. 2

　　　　"110–129 mm", Carapace width of Instar group B