Prevalence and intensity of Anguillicola crassus infection of the European eel, Anguilla anguilla (L.), in Lake Vyrtsjaerv (Estonia)

• Published in: Proceedings of the Estonian Academy of Sciences. Biology, ecology Vol. 51; no. 1; pp. 62 - 73
• Main Authors: Kangur, A, Kangur, P, Kangur, K
• Format: Journal Article
• Language: English
• Published: 01.01.2002
• Subjects: Anguilla anguilla; Anguillicola crassus; Freshwater; Estonia, Vyrtsjaerv L
• ISSN: 1406-0914

Nonindigenous swimbladder nematode Anguillicola crassus was probably introduced into Lake Vyrtsjaerv (Estonia) via importation of live young eels, Anguilla anguilla (standard length of 20-30 cm) from Germany in autumn 1988. Since 1992, the parasite has been found in eels that inhabit this shallow eutrophic lake. The aim of the investigation was to determine the prevalence and intensity of A.crassus infection in the eel population of L. Vyrtsjaerv in different years, and to assess the possible effect of the parasite on eel fishery. Since 1992, 623 eels were examined for Anguillicola. The prevalence of infected eels ranged from 51% to 86% in different years. The average number of worms per infected eel (mean intensity) ranged from 4.0 plus or minus 0.6 in 1999 to 12.6 plus or minus 2.5 in 1993, the maximum number of the parasite was 92 per eel. The mean number of parasites in a swimbladder of eel was not related with the length of the host fish. No statistical difference was found for the condition factor of infected and noninfected fish. Although under normal environmental conditions Anguillicola has not caused serious problems to eels in L. Vyrtsjaerv, high intensity of parasite infection together with other unfavourable factors (e.g. high temperature, oxygen deficiency, intensive algal bloom, etc.) may lead to mass eel kills.