ABSTRACT
In both intertidal and subtidal populations of the fissiparous asteroid, Allostichaster insignis, mean size and the incidence of fission changed little over the course of a 13 month study. Subtidal population density was also quite stable. However, intertidal A. insignis showed some seasonal variation in population density. Starfish are ripe in September and October and the population is composed entirely of males. A second fissiparous starfish species, Coscinasterias calamaria, was less abundant than A. insignis. and both intertidal and subtidal populations were composed of small individuals. Subtidal C. calamaria showed no seasonal trend in fissiparity as measured by the coefficient of variation of arm size. However, intertidal starfish divided more frequently in mid summer which suggests that dessication or thermal stress enhances the incidence of fission.
