Growth and habitat use of the Chinese false gudgeon, Abbottina rivularis, in an irrigation channel near the Ushizu River, northern Kyushu Island, Japan

Information on a population of Abbottina rivularis inhabiting an agricultural ditch was collected during field surveys and was analyzed for age, growth, and habitat use. Measurements of 1,035 individuals revealed that the population had two size classes, a maturation age of 1 year, and a lifespan of 1-2 years. On the basis of the growth pattern and life stage, we classified the life cycle of this species into four stages: the juvenile stage, the immature stage with rapid growth and with no growth, and the adult stage. Habitat use during each stage was analyzed with a generalized linear mixed model. The best fit models revealed that 3-5 environmental factors were important predictors of population size in each stage. In particular, the number of fish increased with increased variation in water depth and with smaller median particle size of the bottom substratum in all stages.