Reducing dietary fish meal levels is required for sustainable aquaculture; therefore, various alternatives, including plant proteins, are being used. Plant proteins sometimes contain fungal toxins such as deoxynivalenol (DON) produced by Fusarium spp. This study investigated the effects of DON on the growth of juvenile yellowtail. In Experiment 1 (7-week trial), three test diets were prepared: a control diet, and a diet with 1.5 and 4.0 mg/kg DON. In Experiment 2 (6-week trial), three test diets were prepared: a control diet, and a diet with 0.1 and 0.5 mg/kg DON. With an average body weight of approximately 20.2 g in Experiment 1 and 6.2 g in Experiment 2, fifteen juvenile yellowtails were housed in each of nine 550 L-capacity fiber reinforced plastic tanks. Feeding was performed once daily until satiation became apparent. Growth performance was reduced at ≥ 1.5 mg/kg diet in Experiment 1 and at 0.5 mg/kg diet in Experiment 2. These results suggest that the minimum toxic dose of DON is considered to be between 0.1 mg and 0.5 mg per kg of feed for juvenile yellowtail.

　Selection curves for eight pelagic fish species were estimated using data from surveys conducted with research driftnets in the Northwest Pacific between 1999 and 2013: pink salmon Oncorhynchus gorbuscha, chum salmon Oncorhynchus keta, coho salmon Oncorhynchus kisutch, yellowtail amberjack Seriola aureovittata, common dolphinfish Coryphaena hippurus, chub mackerel Scomber japonicus, bullet tuna Auxis rochei, and medusafish Icichthys lockingtoni. A series of research driftnets consisting of ten mesh sizes (48, 55, 63, 72, 82, 93, 105, 121, 138, and 157 mm, determined with a geometric ratio of 1.14) were used for the surveys. Pooled relative sampling intensities expressing size selectivity of the research driftnets were then calculated. The results showed that the pooled relative sampling intensity with respect to fork length remained almost constant for six species, excluding coho salmon and medusafish, indicating that the mesh combinations utilized were suitable for the stock survey. However, for chub mackerel and bullet tuna, the number of small fish caught was insufficient due to the few driftnets with smaller mesh sizes. This result suggests that modification of the mesh size combinations, with more of the smaller mesh size nets, is needed to improve the accuracy of the assessment of small fish.

　Adolescent males of snow crabs Chionoecetes opilio molt generally during the peak of the molting season, around September–October each year. However, some of them molt the following molting season (skip molt), or molt during the fishing season, several months after the peak of the molting season (later molt), and they are targeted by fisheries in the Sea of Japan off Kyoto Prefecture. We constructed a new model that considers skip and later molters. Subsequently, we estimated molting probabilities and the biomass of adult males with hard-shell in each instar group. The biomass of adult males decreased as the proportion of skip molting increased, with a particularly significant decline in large adult males. Adolescent males are morphometrically immature and fetch low prices; it was found that the biomass of adult males with high prices would increase by management for adolescent males.

　This study aimed to identify the causative bacteria of white rot disease in cultured nori by subjecting it to infection experiments. Four bacterial strains, which produced comparable symptoms, were isolated from diseased laver thalli. These strains could be reisolated from the infected laver thalli. Three of the four strains were highly virulent, suggesting that they were the major pathogens. The three isolates showed identical 16S rRNA gene sequences. Phylogenetic analysis based on the nucleotide sequences suggested they were most closely related to Aquimarina latercula. This study has identified the causative agent of white rot disease; thus, we propose changing the disease name to “bleaching disease.”