河川水温が両側回遊性コエビ類個体群の越冬に与える影響

抄録

Monthly quantitative sampling of caridean shrimps and prawns, and logging of river water temperatures were undertaken over 13 months in the Kawazu-yatsu and Ogamo Rivers, Izu Peninsula, and the Morito and Shimoyama Rivers, Miura Peninsula, Japan in order to clarify the overwintering status. Low water temperature tolerances of 9 major species were also examined using culture experiments. Water temperatures in the Kawazu-yatsu River were highest throughout the year due to the inflow of hot spring water. Fifteen shrimp and prawn species were collected, the number of individuals tending to decrease in winter in most. In particular, two species, Macrobrachium australe and M.lar, which have low tolerance to low water temperature were found only in autumn in three rivers except Kawazu-Yatsu River, and it was confirmed that they died due to low water temperature in winter. The rate of decline from autumn to winter for the species established in the study area was the lowest in Paratya compressa, which has the highest tolerance to low water temperatures, and in the Kawazu-Yatsu River, which has the highest water temperatures. The decrease in the populations of M. formosense, M japonicum, Caridina leucosticta and C. typus occurred earlier than the decline in river water temperatures, suggesting that they moved to places where it is difficult to collect them, such as deep pools.