Abstract
Population structure, growth, reproductive activities and spatial distribution in a population of the neritid gastropod Clithon retropictus are described, and the effects of habitat stones on distribution and individual activities are investigated. Monthly changes in coupling behavior and abundance of egg capsules indicated that the main reproductive season is June. The occurrence of small juveniles indicated that recruitment occurred mainly between August and September in the lower intertidal region of the adult distribution range. Recruits grew to a large size (ca. 9 mm SL), reaching maturity in June of the second year (ca. 1 year old). Longevity was estimated to be at least 3.3 years. More than 90% of snails occurred on stones throughout the year, predominantly underneath stones on exposed substratum rather than those on submerged substratum. Snail abundance was significantly influenced by stone coverage, water condition and time of year (month). Stone manipulation revealed a positive relationship between snail abundance and stone abundance. Mating behavior occurred mainly on the upper or lateral surface of stones. The occupancy periods of individual snails on stones were positively correlated with stone size in autumn, but not in the other three seasons. Distances moved by individual snails per day were significantly shorter in winter than in the other seasons.
