Sea urchins are economically relevant in fisheries, as the gonads are harvested as a seafood product. Successful aquaculture practices can be enhanced by improving diet formulations, particularly dietary protein sources, which significantly impact growth profiles and gonad quantity and quality (e.g., size, color, texture, flavor). Single-cell protein sources represent a sustainable alternative to current industry standard animal-derived protein sources such as fish and squid meal. In the present study, we evaluated the effects of replacing fish and squid meal with commerically available single-cell dietary protein sources in diets for juvenile Lytechinus variegatus.
Juvenile L. variegatus (ca. 20 g whole-body wet weight, 22 mm test diameter) were collected from Port St. Joe, FL and transported to UAB, where they were housed in recirculating aquaculture systems. Following a 7-day acclimation period, sea urchins were fed one of 7 randomly assigned diets for 8 weeks. Four diets contained protein from only one source: fishmeal (FP), squid meal (SP), bacteria (BP), or yeast (YP). Three diets contained 50% protein from fishmeal and 50% protein from either squid meal (FP/SP), bacteria (FP/BP), or yeast (FP/YP).
Survival was 100% in all treatments. Terminal whole-body wet weight gain was significantly lower in BP-fed urchins compared to all other treatments (Fig. 1A, p<0.002). Terminal gonadosomatic index (GSI) was significantly lower in BP-fed urchins compared to all other treatments (Fig. 1B, p<0.002) except YP-fed urchins. GSI was significantly lower in YP-fed urchins than in FP-fed and SP-fed urchins (p<0.002); however, there were no other significant differences in GSI among any of the diet treatments excluding BP and YP. Overall, the results indicate that the bacteria and yeast proteins used in this study cannot completely replace fishmeal in diets for L. variegatus, but they may be viable as partial replacements for fishmeal. Funded by NSF EDGE.