Aquaculture America 2024

February 18 - 21, 2024

San Antonio, Texas

IT’S NOT THE SIZE THAT MATTERS: STOCKING LARGER CHANNEL CATFISH Ictalurus punctatus FINGERLINGS DOES NOT PROTECT AGAINST PROLIFERATIVE GILL DISEASE

Bradley M. Richardson*, Noor-ul -Huda, Cynthia Ware, Alvin C. Camus, Caitlin E. Older, Fernando Y.  Yamamoto, Penny Goodman,  J.  Grant Riefers, Charles M. Walker, Justin M. Stilwell, David P. Marancik, David J. Wise, and Matt J. Griffin

 

Warmwater Aquaculture Research Unit

USDA – Agricultural Research Service

Stoneville, MS 38776

brad.richardson@usda.gov

 



Proliferative gill disease (PGD) is the leading parasitic disease in US catfish aquaculture. T he causative agent, Henneguya ictaluri, is a myxozoan that most commonly infects fingerling sized catfish and can have devastating impacts on the industry at multiple levels. Management of PGD primarily includes selectively stocking low-risk ponds, based on a species-specific molecular assay performed on pond water samples. This study aimed to evaluate the potential of stocking larger fingerlings to improve survival while also investigating the influence of parasite burden and fish size on three metrics of gill condition. Two industry-relevant sizes of fingerlings ( small: ~12 cm, large: ~20 cm) were stocked into  19 cages located in ponds with known PGD outbreaks. After one week, the fish were removed from the ponds. Water samples were also collected at stocking and removal. At time of removal, m ortalities were recorded, and all survivors were euthanized for gill collection. Gill wet mounts were evaluated for percent  gill damage, number of lesions, and number of presporogonic plasmodia. There was no significant difference in mortality rates between the large and small fingerlings. Generalized linear regression showed no interaction between parasite burden in the pond water or gill tissues and fingerling size. In all regressions, only parasite burden in the pond water or gill tissues was a significant predictor of any gill condition metrics. Results from this study suggest that stocking of larger fingerlings provides no appreciable protection from PGD mortality or sub-lethal gill damage.