MADIGAN, P.A.; WATERS, K.A.; HARRIS, L.G.*: Juvenile Growth Variation in the Green Sea Urchin, Strongylocentrotus droebachiensis: Possible Roles for Larval History, Behavior and Genetics.

Growth of juvenile green sea urchins, Strongylocentrotus droebachiensis, has been observed for three year classes, 1998, 1999 and 2000. The urchins from 1998 and 1999 were collected from juvenile settlement panels set out from May to July at the Isles of Shoals off the New Hampshire coast. The urchins used for the 2000 year class growth studies were obtained from laboratory cultures originating from adults collected at the Isles of Shoals, so all individuals had a similar larval history and settlement date. Throughout the study, urchins were maintained under similar culture conditions and fed a combination of microalgal film and fleshy algae. Animals from 1998 and 1999 were measured for test diameter on a monthly basis, while the animals from the 2000 year class have been measured every two weeks. All three cohorts displayed considerable variation in growth rates under similar culture conditions. Larval history and timing of settlement are two possible explanations for growth rate variation in the wild collected 1998 and 1999 year classes. Genetic variation between individuals is also suggested from the similar patterns of growth variation shown by the laboratory reared 2000 year class. Results also indicate that behavior may be important at high densities, which has implications for aquaculture operations.