Parasite populations of the European eel (Anguilla anguilla L.) in the Rivers Ulla and Tea (Galicia, northwest Spain)

A two-year study was performed of the parasite fauna of the European eel in two rivers, the Ulla and the Tea, in the region of Galicia in northwest Spain, with monthly sampling. A total of 523 eels were captured, and a total of 20 parasite species identified: 7 protozoa (Trypanosoma granulosum, Eimeria anguillae, Myxidium giardi, Myxobolus portucalensis, Hofferellus gilsoni, Ichthyophthirius multifiliis and Trichodina jadranica), 12 helminths (Pseudodactylogyrus anguillae, Pseudodactylogyrus bini, Nicolla gallica, Diplostomum sp., Bothriocephalus claviceps, Paraquimperia tenerrima, Spinitectus inermis, Cucullanus heterochrous, Pseudocapillaria tomentosa, Anisakis simplex L3 larvae, Anguillicola crassus, and Acanthocephalus clavula) and a copepod (Ergasilus gibbus). This is the first report for M. portucalensis, T. jadranica, and P. tomentosa from Spain, and for N. gallica from the Iberian Peninsula. Statistically significant differences in prevalence were observed between the two rivers only in the cases of T. granulosum, T. jadranica, Diplostomum sp. and C. heterochrous. The presence of some species was positively correlated with host body length. Some species pairs showed positive or negative mutual correlations of presence, but only for the pair T. granulosum-Pseudodactylogyrus spp. were there statistically significant correlations in both rivers.