Hiện trạng nhiễm ký sinh trùng ở cá tra (Pangasianodon hypophthalmus) giai đoạn ương giống

Abstract

The study was conducted to determine the current status of parasitic infection in three nursing stages (larval, fry and fingerling stages) of striped catfish (Pangasianodon hypophthalmus). A total of 857 fish (302 samples of larval stage, 218 samples of fry stage and 337 samples of fingerling stage) were sampled from 20 nursery ponds (9 ponds in rainy season and 11 ponds in dry season). The parasitic composition and the infection rate from different nursing stage of fish were examined. Results showed that nine parasite genera (Cryptobia, Trichodina, Balantidium, Apiosoma, Epistylis, Myxobolus, Henneguya, Dactylogyrus, and Gyrodactylus) were found in striped catfish at nursing stage. Besides, cysts of some parasites were identified as Myxozoans, metacercariae of trematodes, larval nematodes and parasitic copepods. Parasitic infection rate was higher in the dry season than the rainy season. In which, the infection rate in dry season was observed at the rate of 56.6%-73.3% in larvae, 50%-100% in fry, 73%-85.7% in fingerlings. The infection rate in the rainy season was observed at the rate of 15%-57.3% in larvae, 40%-100% in fry, 25%-90.3% in fingerlings. In particular, Trichodina, Apiosoma, Epistylis, Myxozoa, Myxobolus, Henneguya spores are commonly found on skin and gills of fish in both dry and rainy seasons. The trend in prevalence and species composition of parasites observed in this study may reflect the specific time of nursing stage to apply interventions in order to reduce the pathogenic impact of the parasites.