Detection of toxins and harmful algal bloom cells in shellfish hatcheries and efforts toward removal

As the start of the supply chain for the aquaculture industry, hatcheries are a crucial component in the success of oyster and northern quahog (hard clam) aquaculture on the East Coast of the US. Intermittent failures in hatchery production slow industry growth and reduce profits. To begin investigations into the possible role of algal toxins in hatchery production failure, post-treatment hatchery water from one research and four commercial hatcheries in lower Chesapeake Bay, USA, was sampled for (1) toxin presence and (2) harmful algal bloom (HAB) cell enumeration. Overall, seven toxin classes, likely produced by six different HAB species, were detected in post- treatment hatchery water, despite a lack of visually identifiable HAB cells within the facility. Toxins detected include pectenotoxin-2, goniodomin A, karlotoxin-1 and karlotoxin-3, okadaic acid and dinophysistoxin-1, azaspiracid-1 and azaspiracid-2, brevetoxin-2, and microcystin-LR. In a second, more targeted study, two batches of source water were followed and sampled at each step of a water-treatment process in the VIMS Aquaculture Genetics and Breeding Technology Center research hatchery in Gloucester Point, Virginia, USA. Two treatment steps showed particular promise for decreasing the concentrations of the three toxins detected in the source water, 24-h circulation through sand filters and activated charcoal filtration. Toxin concentrations of pectenotoxin-2, 3.53 ± 0.56 pg m

Development and evaluation of a formulation of probiont Phaeobacter inhibens S4 for the management of vibriosis in bivalve hatcheries

Abstract Larval eastern oysters (Crassostrea virginica) grown in shellfish hatcheries are susceptible to bacterial diseases, particularly vibriosis. Probiotics are microbes that confer health benefits to the host and have been identified as promising tools to manage diseases in aquaculture. The marine bacterium Phaeobacter inhibens S4 (S4) protects larval eastern oysters against challenge with the bacterial pathogen Vibrio coralliilyticus RE22 (RE22). A concentrated liquid formulation of probiont S4 that maintained high cell viability after long‐term storage was developed for commercial use in shellfish hatcheries. The safety and efficacy of the formulation were tested in six different trials in two hatcheries. The S4 formulation was added to C. virginica larvae culture tanks daily at 104 colony forming units (CFU)/mL from Day 1 post fertilisation until Day 6, 12 or 14, depending on the trial. Treatment of larvae in the hatchery with the S4 formulation did not significantly affect the survival and growth of the larvae. Formulated probiont S4 treatment in the hatchery led to a significant increase in relative percent survival (RPS) when larvae were subsequently challenged with the pathogen RE22 (105 CFU/mL) for 24 h in a laboratory challenge as compared to probiotic‐untreated RE22‐challenged larvae (RPS increase of 46%–74%, p < 0.05). These results suggest that this novel S4 formulation is a safe, easy‐to‐use and effective tool in preventing larval losses due to vibriosis in hatcheries