INTEGRATED AQUACULTURE OF SEA URCHINS (LYTECHINUS VARIEGATUS) AND SHRIMP (LITOPENAEUS VANNAMEI)

Shrimp (Litopenaeus vannamei) were provided access to sea urchin (Lytechinus variegatus) egesta to investigate whether fresh egesta (containing an active microbiome) consumed alone or in combination with a commercial shrimp feed could influence growth, feed conversion, body composition, and survival of L. vannamei in co-culture. In an initial experiment conducted for 8 wk, shrimp were proffered a full or reduced ration (100%, 60%, and 20%) of commercial shrimp feed with or without access to sea urchin egesta serving as a source of supplemental nutrients and presumptive probiotics. Individual weight gain of shrimp provided sea urchin egesta only (10.37 [+ or -] 0.35 g) did not differ significantly from that of shrimp proffered a full ration of feed (9.46 [+ or -] 0.39 g) despite significant compositional differences. Consumption of sea urchin egesta combined with commercial shrimp feed resulted in significantly greater weight gain of shrimp when compared with shrimp proffered the same level of commercial shrimp feed only. The largest weight gains of shrimp were found for those groups fed rations of 60% and 100% and had access to egesta (14.09 [+ or -] 0.75 g and 14.72 [+ or -] 0.68 g, respectively). In the next experiment, shrimp were stocked at different densities (approximately 23, 45, 68, and 90 individuals [m.sup.-2]) and were not proffered feed directly. All replicates were provided access to fresh sea urchin egesta produced by four urchins that were fed at a daily rate of 3% of the total initial group weight (140.4 [+ or -] 0.7 g) for 8 wk. The largest individual weight gain was found in the lowest density treatment (6.55 [+ or -] 0.38 g). Harvested biomass significantly increased as density increased, except for the highest density treatment. These results indicate that sea urchin egesta may provide some growth enhancement factor(s) to shrimp when proffered in conjunction with a commercial diet, and at a certain density of shrimp sea urchin egesta may actually serve as a nutritionally complete diet. KEY WORDS: Lytechinus variegatus, Litopenaeus vannamei, co-culture, egesta, integrated aquaculture, sea urchin, shrimp
INTRODUCTION A previous study (Jensen et al. 2018) suggested that fresh egesta (fecal pellets) produced by sea urchins (Lytechinus variegatus) served as a sufficient source of nutrition for cocultured Litopenaeus [...]