Survivorship and growth rates of hatchery-reared sea urchins

The survivorship and growth rates of juvenile, hatchery rearedPsammechinus miliaris (Gmelin) were observed for seaurchins fed different diets, and maintained at varying stocking densities andlocations (tank or sea-based). In addition survivorship and growth of secondgeneration hatchery stock was also recorded. Somatic growth rates of juvenileurchins (initial test diameter 6.5 mm SD 1.26) were measured over9months. A high lipid, high protein diet supported higher somatic growth ofurchins in this size range. Higher stocking densities (4 individualsl^–1 as opposed to 2 individuals l^–1)adversely affected growth as did location (sea-based urchins being smaller thantank based) although survivorship in all treatments and in both first andsecondgenerations was exceptionally high. Further research is required to designdietspromoting somatic rather than gonadal growth in urchins below market size.