In the 1990s, a reduction of Japanese chum salmon (Oncorhynchus keta) body size was observed. In order to investigate this body size reduction of Japanese chum salmon in the North Pacific, we developed a bioenergetics model for chum salmon. Our model was based on NEMURO.FISH, using respiration and consumption terms and assumed that SST and prey zooplankton density are the determining factors of the reduction of body size. SST and prey zooplankton density are obtained from the result of NEMURO embedded in 3-D physical model, along the migration route of chum salmon. The period of foraging migration is supposed to be four years and the life stage of Japanese chum salmon is divided into eight stages, i.e. four stages for summer and the other four for winter. The model reproduced the body size of the 1972 and 1991 year classes of chum salmon, respectively. Reproduced body size of the 1972 year class was larger than that of 1991 year class. This result showed a good agreement with the observations in the Bering Sea. Moreover, our model reproduces the trend of observations in l970—2000 well. The prey density, especially in the Eastern North Pacific, had a larger influence on the change of body size than SST did. This suggested that the size reduction of Japanese chum salmon in the 1990s was partly affected by prey zooplankton density.

We studied the trend of long-term fluctuation in the abundance of abalone and top shell catch in Japan and examined the relationship of those long-term fluctuations with global climate change. Trend of fluctuation index (TFI) was derived from time-series of yearly catch in five sea areas around Japan by removing the dependence of amplitude of catch fluctuation on its level and calculating the slope of regression line at each year. Approximately two decadal scale fluctuations were found in TFI of each resource. There were significant positive correlations between TFI of three abalone species (Haliotis discus discus, H. gigantea, H. madaka), which inhabit in four sea areas influenced by the warm currents, and moving means of Aleutian Low Pressure Index (ALPI). In two sea areas along the coast of the Pacific, TFI of these three abalone species was positively correlated also with that of agar, red algae belonging to the Gelidiaceae. In contrast, TFI of H. discus hannai, which inhabits in one sea area influenced by the cold current, was negatively correlated with ALPI or TFI of agar. We could not find any coherent relationship of TFI of top shell, Turbo (Batillus) cornutus, with ALPI or TFI of agar. The results of this study suggest the possibility of the influence of global climate change to the long-term fluctuation in the abundance of rocky shore resources, which have been thought to be “local” stocks, and of the difference of such influences among species.

This paper describes the distribution of catches of diamond squid (Thysanoteuthis rhombus) off Hyogo Prefecture in the western Sea of Japan, and the relationship between the fishing condition and seawater temperature based on the catchlocation and catch-amount data collected from the logbooks of seven vertical longline fishing boats in 1999-2005. Catches generally occurred south of 36°15’N, but in September-October of 2003 and 2005, when a cold water mass occurred on the fishing ground, catches were concentrated near shore south of 35°45’N. Good catches occurred where seawater temperatures at 50 and 100 m depths were>19°C and>14-15°C, respectively, from late August through early November in 1999-2005. The mean water temperature at 100 m depth at six oceanographic observation sites off Hyogo Prefecture was related to the mean latitude of catch locations weighted by catch amount, which suggests that this index can be used to forecast the location of the fishing grounds.

Coral reef ecosystems in Sekisei Lagoon, the largest coral reef complex in Japan, suffered from coral bleaching phenomena caused by elevated seawater temperature in 2001 and 2003. To investigate temperature environments during the bleaching events, seasonal changes in 3-m seawater temperature recorded at two fixed survey stations between 1998 and 2003 were analyzed with those in atmospheric temperature recorded at Ishigaki Island. The total number of days of which both daily average seawater temperature and daily average atmospheric temperature exceeded 30°C in 2001 and 2003 were larger than those in the other years. Accordingly the atmospheric temperature data in the past three decades were analyzed using an assumed bleaching subtracted temperature of 30°C and an index that was defined as a sum of the surplus value exceeding 30°C (the accumulated coral bleaching subtracted atmospheric temperature). The results indicated that coral bleaching can occur when a total number of days of which daily atmospheric temperature exceeded 30°C is larger than 30, and the accumulated coral bleaching subtracted temperature is larger than 10.