The distribution of the invasive shrimp Neocaridina davidi (Decapoda: Caridea: Atyidae) in relation to environmental parameters in a stream at Kunitachi, Tokyo, Japan

抄録

The distribution of the invasive freshwater shrimp, Neocaridina davidi, in a spring-fed stream at Kunitachi, Tokyo, Japan, was investigated in relation to the stream’s environmental parameters. Compared to previous studies, the population density of N. davidi was found to be remarkably high (up to 315 ind./m²). The increase in population density is likely because the water temperature in the spring-fed stream remains 17–20°C in the winter, prolonging the period during which the shrimps can spawn. Generalized linear mixed models showed that adult shrimps were more abundant in areas with high emergent plant coverage. In contrast, juveniles were more abundant in areas with low current velocity. These results provide essential clues to the interspecific relationships between N. davidi and native spring organisms that inhabit the same physical environments.