The net productions of communities of the warm temperate kelp Ecklonia radicosa in Izu-Oshima Island, central Japan were estimated by hole-punch and photosynthetic methods. The net production by the hole-punch method exceeded that by the photosynthetic method from March to July. From August to September, the net production by the photosynthetic method exceeded that by the hole-punch method as the light conditions improved. Theoretically, the net production by the photosynthetic method should always exceed that by the hole-punch method, but the results of this study did not support this theory. Therefore, we conclude that it is necessary to reconsider the relations of leaf arrangement for each growth stage of individual plants and light conditions in plant communities for single-blade species of laminariales.

　The seasonal vertical distribution and biological characteristics of North Pacific giant octopus Enteroctopus dofleini were investigated using box-fisheries data in the Sea of Japan off the coast of northern Hokkaido between 2006 and 2011. The results showed that the depth distribution of E. dofleini was >50 m from August to September, <40 m from October to December, 30-60 m from January to February, <30 m from April to May and 20-50 m from June to July. Most individuals were immature with body weights ranging from 2.5 to 10.0 kg (mean 5.7 kg). The most abundant food items included Urechis unicinctus, various fish, crabs, and octopus. The results showed that immature octopuses in this fishery appear to undertake two seasonal migrations per year.

　Diarrhetic shellfish poisoning (DSP) refers to a gastrointestinal disease following the ingestion of bivalve shellfish containing dinoflagellate toxins of lipophilic nature collectively referred to as okadaic acids (OAs). OAs strongly inhibit protein phosphatase 2A (PP2A) and thus are quantifiable by measuring the extent of the enzyme inhibition. We recently produced the recombinant catalytic subunit of human PP2A (rhPP2Ac) by genetic engineering techniques using the baculovirus expression system with High Five insect cells. In this study, we evaluated the suitability of rhPP2Ac for use in a microplate OA assay. The limits of detection and quantitation for OA in the whole meat of the scallop Patinopecten yessoensis were 0.0262 mg/kg and 0.0470 mg/kg respectively, which are well below the regulation level in Japan (0.16 mg/kg whole meat). Differences in lipid content of the scallop did not affect the measurement result. Our results confirm that the assay kit using rPP2Ac is an excellent tool for detecting and quantifying OAs in shellfish.

　Effects of climate change on the long-term fluctuation in the catch of abalone Haliotis discus hannai along the west and south coasts of Hokkaido, the northern limit of its distribution, were examined. The trend of fluctuation index (TFI) for the transformed abalone catch (Catch-TFI) showed a negative correlation with TFI for Aleutian Low Pressure Index (ALPI-TFI) in the northern Japan Sea Coast. Catch-TFI in the southern Japan Sea Coast presented positive correlations with the ALPI-TFI, and showed negative correlations with the TFI for the Arctic Oscillation Index (AOI-TFI), the same as the western Tsugaru Strait Coast. Changes in sea water temperature in winter controlled by climate change appear to affect the fluctuation of abalone fishery resource in various ways depending on the area on the coast of Hokkaido, through the survival rate of juvenile abalone and seaweed production affecting the egg production of adult abalone.

　Discharging rates as well as nutrient and dissolved metal concentrations were measured for the submarine groundwater discharging around Ohkurokami Island (Hiroshima Prefecture) and Suo-ohshima Island (Yamaguchi Prefecture). Concentrations of dissolved materials were high in the submarine groundwater compared to those in the surrounding bottom seawater. Although the areas where the submarine groundwater is discharging estimated by divers were almost the same in both locations, the water discharge rate was 2.5 times higher and the concentrations of dissolved materials were 2 orders of magnitude higher at Suo-ohshima Island than at Ohkurokami Island. Referring to the Redfield ratio, the water around Ohkurokami Island is abundant in N and Si but low in Fe, while the water around Suo-ohshima Island is abundant in Si and Fe, but low in N. These submarine discharges of groundwater may influence the formation of specific biota and production in these two areas.

　Spotted mackerel Scomber australasicus caught in purse seines in Kagoshima are commonly rested for a few days in fish cages without being fed so as to reduce the stress of capture. They are then killed instantaneously and distributed in Kagoshima Prefecture as high-quality sashimi (raw fish meat). We determined the acceptable period of time for which the fish could be rested unfed in fish cages while still maintaining their high quality as sashimi. To do this, we analyzed the condition factor, various body components such as plasma, and muscle properties. The content of fat in the muscle did not decrease. The content of protein in the muscle decreased. The elastic strength of the muscle was maintained until day 21. The condition factor did not decrease until day 15; it was significantly lower after day 15 than on the day when resting began. These data indicate that spotted mackerel can be rested unfed in fish cages for up to 15 days before their quality as sashimi declines.