Population dynamics and production of Jesogammarus annandalei, an endemic amphipod, in Lake Biwa, Japan |
| |
Authors: | Toshiyuki Ishikawa Jotaro Urabe |
| |
Institution: | Center for Ecological Research, Kyoto University, Otsu, Shiga, Japan |
| |
Abstract: | SUMMARY 1. Population dynamics and production of Jesogammarus annandalei , an endemic amphipod in Lake Biwa, were examined from April 1997 to June 1998. The life cycle of this species was 1 year with the new generation beginning in early autumn. They preferred low temperature (<12 °C) and their spatial distribution varied seasonally and accordingly. 2. In deep water, the abundance of J. annandalei ranged from 200 to 63 000 m−2 and decreased towards summer and the biomass (0.01∼3.6 g C m−2) was on average comparable that of zooplankton. The density was much higher than that recorded by a study conducted 35 years ago. 3. Individual growth rate of this amphipod was high in winter and spring but decreased in summer. Annual production of J. annandalei (6.2 g C m−2 year−1) was only 2% of primary production but was at the higher end of the range reported for amphipods in oligo- and mesotrophic lakes. 4. These results are consistent with the view that Lake Biwa is becoming more eutrophic, with a consequent decrease in the abundance of predatory fish in the profundal zone. |
| |
Keywords: | amphipod endemic species large lake macrobenthos secondary production |
|
|