Infection of the Fish Species Perca fluviatilis, Stizostedion lucioperca and Esox lucius with Eustrongylides excisus Jagerskiold, 1909 (Nematoda: Dioctophymatidae) in the Lower Section of the Dniprovske Reservoir: Site Preference and Pathogenicity

A helminthological survey of three fish species (Perca fluviatilis, Stizostedion lucioperca and Esox lucius) from the lower section of the Dniprovske Reservoir (also known as Zaporizhzhia) revealed the presence of the dioctophymatid nematode Eustrongylides excisus (third stage larvae). The study was conducted in 2020 and 2021. It was found that the total prevalence of infection was more than 40%. The nematode was found in the liver, abdomen and muscles. Significant tissue lesions were observed in some fish specimens. They were visually accompanied by mechanical damage, oedema and inflammation. The intensity of infection in P. fluviatilis and S. lucioperca was 14.18 +/- 0.81 and 12.69 +/- 0.73, respectively. In turn, the intensity of infection in E. lucius had the lowest value 2.40 +/- 0.41. The abdomen and muscles of P. fluviatilis and S. lucioperca were affected more than the liver. No statistically significant differences were found between the intensity of infection of the abdomen and muscles in P. fluviatilis. Furthermore, the musculature of S. lucioperca was more heavily infected than the abdomen. In E. lucius, nematodes were found only in the abdominal cavity.