Methods for the Prevention and Control of Glochidiosis in Yellow Catfish Aquaculture

[Cause] The pathogen is the glochidium larva (Glochidium sp.). The fertilized eggs of mussels develop into glochidia in the outer gill cavity of the mother mussel, then leave the parent and float in the water; after contacting the fish body, they parasitize on the fish. The larvae undergo metamorphosis by absorbing nutrients from the fish body and develop into young mussels.

[Symptoms] The glochidia attach to the fish body with their byssal threads, hooking onto the fish's mouth, gills, fins and skin with their shell hooks. The fish body is stimulated, causing tissue inflammation and proliferation, which gradually envelops the larvae and forms cysts.

[Epidemiology and Harm] The disease is mainly prevalent in late spring and early summer, which is exactly when the glochidia leave the parent and become suspended in the water. The yellow catfish is the most ideal host for the glochidia. A small number of larvae generally has little effect on larger adult fish, but has a greater impact on fry and summer-fingerling fish. After the glochidia parasitize the gills, oral cavity and other parts of yellow catfish fingerlings, the fingerlings lose their feeding ability and starve to death, or suffocate and die because breathing is impeded.

[Diagnosis] (1) A preliminary diagnosis can be made based on the symptoms of the diseased fish. (2) Remove the cysts from the fish body and observe the glochidia under a dissecting microscope to confirm the diagnosis.

[Prevention and Control] (1) Thoroughly clear the pond with quicklime. Or use 60-80 mg/L of tea seed cake to kill the mussels in the pond. (2) Mussels must not be co-cultured in fry and summer-fingerling rearing ponds, and the inlet water should be filtered through nets to prevent glochidia from entering the pond with the water. (3) In the early stage of the disease, transfer the diseased fish to a pond without mussels and glochidia, which can control the development of the disease and lead to gradual improvement.