THE EFFECT OF DIFFERENT NUTRIENT FORMULATIONS IN ARTIFICIAL DIETS ON GONAD GROWTH IN THE SEA-URCHIN STRONGYLOCENTROTUS-DROEBACHIENSIS

Several artificial diets were tested for their ability to promote grow th of gonads in the green sea urchin, Strongylocentrotus droebachiensi s, over a 9-month period. Survival and test growth were also monitored , as were gonad lipid levels and water content (at the middle and end of the reproductive cycle only). The artificial diets differed in amou nt of protein and in the presence of various additives such as mannito l, algin, cholesterol, and beta-carotene; a diet of air-dried kelp (Ne reocystis luetkeana) was included for comparison. Survival was >95% fo r all diets save a low-protein one (82% survival). Test diameters show ed no significant change over time or among dietary treatments. All hi gh-protein formulations produced significantly higher gonad indices th an low-protein ones. Addition of beta-carotene to the high-protein for mulation significantly increased gonad growth relative to all other di ets; this was especially noticeable in December, at the time of best m arket quality for the roe. Lipid levels were not significantly differe nt among dietary treatments in either November or March, but did show a slight statistically significant rise between these months (21.4-22. 7% dry mass). Water content also showed no significant difference amon g treatments, but was significantly higher in March (82% live weight), just prior to spawning, than in November (70%). Gonad indices for all artificial-diet formulations were higher than any previously recorded for S. droebachiensis.