Comparative assessment of metazoans infestation of Nile tilapia (Oreochromis niloticus) (L.) (Perciformes: Cichlidae) in floating cages and ponds from Chiapas, Mexico.

Nile tilapia is the most commercially important fish in Chiapas as well as in other parts of the world. An understanding of parasite infection dynamics in tilapia may assist in applying proper prophylactic measures for reducing the loss of fish caused by parasitic diseases. Different environments and culture systems may imply different infection dynamics; therefore, the present study identified and compared the infection parameters (prevalence, mean abundance, and intensity) of parasites of Oreochromis niloticus cultured in floating cages and ponds. A total of 18 metazoan parasite taxa were recovered from gills, skin, fins and intestines of 310 specimens from floating cages and ponds. Fourteen species of parasites were found in floating cages: 8 monogenean species, 1 nematode, 1 digenea, 1 crustacea, 3 protozoans. In ponds, 16 parasite taxa were reported: 11 were monogeneans species, 4 protozoans and 1 crustacean. In both systems, monogeneans (Cichlidogyrus sclerosus, C. tilapiae, Gyrodactylus cichlidarum) and protozoans (Trichodina compacta) were most prevalent. Tilapia in ponds sustained higher parasitic infections than those in floating cages (p < 0.05). The Canonical Correspondence Analysis showed two groups: the first grouped the ponds, associated with high values of nitrite, nitrate, ammonia, conductivity, temperature, and the abundance of the ectoparasites C. halli, C. dossoui, Scutogyrus longicornis, C. sclerosus and T. compacta. The second group grouped the cages, associated with Clinostomum marginatum, Apiosoma piscicola, Lernea sp., and Contracaecum sp. and a high dissolved oxygen concentration. Our findings suggest that monitoring programs are required to improve the sanitary conditions of tilapia cultures in Chiapas.