A greater understanding of dietary protein and carbohydrate levels with regard to gonad production in Strongylocentrotus purpuratus would increase our nutritional knowledge of this sea urchin and guide the development of formulated diets for such aquaculture target species. A total of 255 purple sea urchins were captured from Ensenada Bay, Mexico, and maintained in 200-L tanks for 9 weeks. Formulated diets that contained 30%, 26%, 23%, 20% and 17% of protein and 42%, 46%, 50%, 54% and 58% carbohydrates were offered ad libitum. Survival was affected by diets; urchins that were fed high-protein-low-carbohydrate diet experienced decreased survival. No significant differences were found in gonad index, but gonad production efficiency was lower in urchins that were fed a medium-low-protein-medium-high-carbohydrate diet. Urchins that were fed high carbohydrate levels utilized protein more efficiently and showed better digestibility of the diet and protein. These data suggest that all of our diets support gonad growth, but in terms of consumption, a diet that contains protein levels of 17% and 23% with carbohydrate levels of 50% and 58% are beneficial for S. purpuratus.

Increased gonad growth of the purple sea urchin (Strongylocentrotus purpuratus) fed the giant kelp (Macrocystis pyrifera) and the sea lettuce (Ulva lactuca) enriched with nutrients Abstract Adult (Strongylocentrotus purpuratus) purple sea urchins were fed giant kelp (Macrocystis pyrifera) and sea lettuce (Ulva lactuca) macroalgae that were unenriched and enriched with nutrients. Urchins were fed over 10 weeks (5% body weight per day) under laboratory conditions to determine the effect of macroalgae species and treatment (enriched and unenriched) on growth, gonad index and gonad quality. Significant differences were observed when urchins were fed enriched Macrocystis pyrifera (MPE). Gonad weight increased from 0.7 AE 0.1 g (mean AE SD) to 5.9 AE 1 g, and gonad index increase from 3.5 AE 1.5% to 14.9 AE 2.3% over 10 weeks. Significant differences were also noted in gonad quality, and gonad colour and firmness were better in urchins that were fed unenriched M. pyrifera (MPUE) and MPEwhereas texture did not differ between M. pyrifera treatments and unenriched U. lactuca (ULUE). With regard to taste, gonads were sweeter in MPE-fed individuals. Enriched U. lactuca (ULE) failed to grow gonads significantly; as a result, their quality was unacceptable for the market. These results suggest that S. purpuratus experience increased gonad production and quality in short periods when fed nutrient-enriched M. pyrifera.

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Understanding the nutritional requirements of the purple sea urchin Strongylocentrotus purpuratus is essential for producing suitable formulated diets and promoting its aquaculture in Mexico. Protein and carbohydrates are required components for gonad growth in sea urchins, yet their levels and effects on gonad composition and color have not been determined for this species. The effects of dietary protein and carbohydrates on gonad index, consumption, proximate content, and color were investigated in S. purpuratus in a 12-week experiment, from April to June 2015. Sea urchins were collected from Arbolitos Bay in Ensenada, Baja California, Mexico, and fed diets that contained three protein levels (300, 230, and 170 g/kg) and two carbohydrate levels (420 and 500 g/kg). All diets significantly increased gonad index, but individuals that were fed a diet with 300 g/kg of protein and 500 g/kg of carbohydrate had the highest gonad index. Dietary protein had a significant effect on lipid storage, whereas protein and nitrogenfree extract storage had no significant relationship with dietary protein or carbohydrate. Differences between gonad color and the standard color cards indicated that S. purpuratus gonads tended to be closer to an orange-yellow color. This study indicates that S. purpuratus will have increased gonad index values at all protein and carbohydrate quantities that were tested in this study. However, gonad coloration is more suitable with a diet containing 230 g/kg of protein and 500 g/kg of carbohydrates.

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