Aggregation for spawning in the breeding season of the sea-star, Asterina minor Hayashi

A field study was conducted to determine the breeding season, process of spawning aggregation and dispersal, and biomass, by the quadrat method in the sea-star, Asterina minor at Echizen Coast in Fukui Pref., Japan. The breeding season of this sea-star was between late May and early June. Individuals more than 100mg in wet weight and a major radius of more than 4mm were mature. The highest values of density, biomass and overlapping were 11.4/m², 13114mg and 14.9%, respectively, and were observed during the breeding season. Overlapping occured only during the breeding season. Mature, large sea-stars aggregated shortly before spawning and overlapping continued for about 2 weeks. After spawning, they dispersed quickly.