The effect of different nutrient formulations in artificial diets on gonad growth in the sea urchin Strongylocentrotus droebachiensis

Abstract

Several artificial diets were tested for their ability to promote growth of gonads in the green sea urchin, Strongylocentrotus droebachiensis, 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 amount of protein and in the presence of various additives such as mannitol, algin, cholesterol, and β-carotene; a diet of air-dried kelp (Nereocystis luetkeana) was included for comparison. Survival was > 95% for all diets save a low-protein one (82% survival). Test diameters showed no significant change over time or among dietary treatments. All high-protein formulations produced significantly higher gonad indices than low-protein ones. Addition of β-carotene to the high-protein formulation significantly increased gonad growth relative to all other diets; this was especially noticeable in December, at the time of best market quality for the roe. Lipid levels were not significantly different 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 among 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.