Utilization of Algal Turf Scrubber Biomass in Sea Urchin (Lytechinus variegatus) Diets

This study evaluated the growth indices in sea urchins fed varying levels of algal turf scrubber (ATS) biomass for the partial replacement of dietary menhaden fishmeal. Juvenile Lytechinus variegatus were fed four formulated diets with differentiating levels of ATS biomass (10%, 10%, 20%, and 50%). Biomass was harvested from two ATS systems, one receiving treated wastewater effluent and the other incorporated into a hydroponics system. A 12-week growth trial was conducted, and each sea urchin (n = 100) was weighed and fed daily. Diets were formulated using Agri-Data Systems Pro 5 (Version 2.41, Agri-Data Systems). Four isonitrogenous and isocaloric diets were prepared. At the end of the growth trial, no significant differences were found in final weight, final diameter, and survival across all diets. All treatments performed well based on condition level and higher levels of ATS biomass did not indicate reduced growth or dietary utilization. Final weights of dry test, and dry gut, were not significantly different between treatments, except for dry gonad compared with menhaden fish meal. These findings indicate that in sea urchin diets, partial replacement of fish meal with ATS biomass is well tolerated.