EFFECT OF PROBIOTICS ON LARVAL SURVIVAL, GROWTH, AND SETTLEMENT SUCCESS OF THREE SHELLFISH SPECIES

Shellfish aquaculture relies on a consistent supply of larvae for restoration, research, or mariculture. Research investigating the addition of probiotics, consisting of viable microbial spores or live microorganisms, has been shown to enhance growth, survival, and disease immunity in a variety of shellfish species. Commercially available probiotics are widely used in the shrimp industry, but these products have not been evaluated for bivalve culture. Previous studies have reported Bacillus sp. can enhance the production of Crassostrea (oyster) and Argopecten (scallop) species. This study identified whether a readily available probiotic comprised of Bacillus sp. would improve growth, survival, and competency for multiple commercial shellfish species in the Gulf of Mexico: the eastern oyster (Crassostrea virginica), bay scallop (Argopecten irradians), and hard clam (Mercenaria mercenaria).

Larval cultures closely mimicked commercial densities and techniques used in shellfish aquaculture. Treatments consisted of a control (no probiotic), high probiotic (), and low probiotic () each consisting of three replicates. Seawater treated with probiotics was ‘aged’ for 24hr prior to larval addition. Survival counts were recorded every two days, and images were captured for growth measurements. Competent larvae were harvested, counted, and settled in replicated downweller systems. Seed were counted after a grow-out period of two weeks.

C. virginica cultures had the most benefit from probiotic additions, with an increased larval survival and growth rate in both probiotic treatment levels (P <0.05) in the fall culture and an increased survival rate (P <0.05) in the spring. M. merceneria and A. irradians cultures lacked significant increases in growth and survival during the larval phase. However, the M. merceneria fall culture reported a significant increase in competency and seed production in probiotic treatments compared to controls. These results suggest species-specific enhancements are shown for some bivalves when using commercial probiotics marketed for other species.