Species richness of exotic and endangered fishes in Japan’s reservoirs

Abstract

We analyzed the patterns of total, endangered and exotic fish species richness in 80 reservoirs throughout Japan using Generalized Linear Models (GLMs) with variables of dam characteristics (e.g. reservoir size, isolated period, altitude, DO, pH, rainfall, and air temperature) and watershed characteristics (e.g. watershed area, human population, and land-use patterns). Exotic species richness was positively correlated with total species richness but negatively correlated with endangered species richness. Largemouth bass, rainbow trout, and bluegill were the three most widely distributed species, occupying 47.5, 37.5, and 33.8% of the reservoirs, respectively. The patterns of total and endangered species richness were largely explained by watershed area and annual air temperature. Exotic species richness was determined primarily by the proportion of developed areas within each watershed. Therefore, reservoirs in more developed areas tend to support more exotic fish species that in turn threaten endangered fish species more severely.