PARENT SESSION
Poster Session 19: Biodiversity
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Effects of dams on freshwater fish diversity and distribution in Hokkaido, Japan.
Fukushima, Michio*,1, Kameyama, Satoshi, 1 National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan
ABSTRACT- Dams pose serious threats to aquatic organisms and biodiversity by fragmenting streams and rivers into small habitats and acting as barriers to passage between these habitats. We assessed the effects of damming on freshwater fish assemblage structure in Hokkaido, Japan. A series of regression models were fitted to fish occurrence and species richness data collected at 125 sites in Hidaka, southern Hokkaido, and to data collected over the last 50 years during 6674 fish surveys conducted throughout Hokkaido. Of the eight dominant fish species sampled in Hidaka, all of the six diadromous fishes were adversely affected by dams, whereas two strictly freshwater species were not affected. In particular, small benthic diadromous species of gobiids and cottids were severely affected by dams regardless of fishway existence, suggesting the limited efficacy of fishways as a mitigation device. Throughout Hokkaido, fish species richness was also significantly influenced by dams after the effects of altitude, sampling year, and other environmental factors were accounted for by the models. The predicted loss of species richness due to damming increased with decreasing elevation, reaching a maximum loss of nine species at river mouths. Areas throughout Hokkaido where fish species richness had potentially decreased were predicted and mapped; the loss of species richness was predicted to be on average 12.9%. Of 43 fish species individually examined in this study, 26 were found to be influenced by damming, and 10 of these were directly and negatively affected. This study provides a comprehensive look at the effects of damming on freshwater fish, through the examination of numerous species with various life histories on a large spatial scale, covering an area of approximately 78 500 km2.
Key words: habitat fragmentation, species richness, freshwater fish assemblages, predictive models