Evaluation of snail trap prototype for monitoring the intermediate gastropod hosts of Bolbophorus spp. in commercial catfish ponds in the southeastern United States

Authors: Richardson, Brad; REIFERS, J. - Mississippi State University; WALKER, CHARLES - Mississippi State University; BYARS, TODD - Mississippi State University; MISCHKE, CHARLES - Mississippi State University; GRIFFIN, MATT - Mississippi State University; WISE, DAVID - Mississippi State University

Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2023
Publication Date: 4/14/2023
Citation: Richardson, B.M., Reifers, J.G., Walker, C.M., Byars, T.S., Mischke, C.C., Griffin, M.J., Wise, D.J. 2023. Evaluation of snail trap prototype for monitoring the intermediate gastropod hosts of Bolbophorus spp. in commercial catfish ponds in the southeastern United States. Journal of the World Aquaculture Society. 54(5):1247-1259. https://doi.org/10.1111/jwas.12962.
DOI: https://doi.org/10.1111/jwas.12962

Interpretive Summary: Bolbophorus damnificus is an important detrimental parasite in the US catfish aquaculture industry. The parasite has a complex life cycle that incorporates fish-eating birds, aquatic snails, and fish as hosts. As no therapeutic treatments are currently available for parasite infections, control is limited to breaking the life cycle through management of the hosts, particularly the snail host. However, more information is needed to reliably target snail treatments when the parasite risk is highest. In an effort to better estimate snail abundances in catfish ponds, scientists at USDA, ARS, Warmwater Aquaculture Research Unit and Mississippi State University distributed a snail trap prototype into food fish and fingerling ponds on a commercial catfish farm. Traps were checked weekly throughout the production season. Additionally, the pond banks were sampled monthly to correlate snail abundance in the pond and in the traps. Traps collected as many as 800 snails on a given day and showed different abundance patterns between food fish and fingerling ponds. Preliminary testing of the snail trap prototypes show promise for their use by farmers as a passive means for monitoring snail populations to better inform treatment timing for control of Bolbophorus infections.

Technical Abstract: Bolbophorus damnificus is a digenetic trematode causing significant economic losses within the United States commercial catfish industry. The indirect life cycle is complex, requiring piscivorous birds, aquatic snails, and fish to complete. With federal protections on many piscivorous birds and no FDA-approved therapeutic treatment for parasite infestations in fish, management within the catfish industry is primarily limited to controlling the snail host. Two pulmonate snails (Planorbella trivolvis and Biomphalaria havanensis) are commonly found in commercial catfish ponds and known to transmit B. damnificus. Though several studies have investigated potential pond treatments for controlling snail populations, basic biological and ecological information about these snails in these systems is lacking. This study evaluated a low-cost snail trap prototype for monitoring populations of P. trivolvis and B. havanensis in efforts to better inform treatment regimes. Snail traps were deployed into ponds on a commercial catfish farm and checked weekly throughout the production season. Also, semi-quantitative sampling was conducted monthly within each pond using a 1-m2 box trap and a D-frame net. All snails were identified and counted to evaluate trap efficacy. A model was constructed to estimate snail densities along pond margins using biotic and abiotic variables. Traps captured significantly more snails in food fish ponds than fingerling ponds; however, this trend was not present in monthly box samples. B. havanensis was rarely collected and was only found consistently within one pond, while P. trivolvis was routinely collected from all ponds, though abundance varied widely among ponds on a given day. The constructed model was relatively accurate at predicting shoreline snail densities, yielding a 0.72 R^2 using bootstrapped estimates. Snail traps could be a useful, low-cost method to monitor snail populations within ponds. Information derived from snail traps can help farm managers make more informed decisions regarding when to initiate pond treatments and maximize treatment efficacy, thereby yielding better treatment results, reducing treatment costs and ultimately lowering risk of parasite infestation.