Habitat-specific variations in Anguillicola crassus infection in the European eel (Anguilla anguilla) from Lake Shkodra and Karavasta Lagoon, Albania

Year 2025, Volume: 8 Issue: 2, 101 - 108, 29.12.2025

Marco Kule Edmond Hala

https://doi.org/10.46239/ejbcs.1822311

Abstract

The European eel (Anguilla anguilla) faces numerous threats, both human-induced and ecological, which have led to a decline in its population. Among these threats, the nematode Anguillicola crassus impacts the swim bladder of the European eel, complicating its migration to breeding grounds.The current study compares the biometric parameters and the parasitic infestation situation with A. crassus in two of the most important eel fishing habitats in Albania. The transboundary Lake Shkodra/Skadar (freshwater lake) and Karavasta Lagoon (brackish water lagoon). A total of 297 silver-stage eels were sampled between December 2024 (141 from Lake Shkodra and 156 from Karavasta Lagoon). For each site, biometric data were measured and sagittal otoliths were extracted for age estimation. The prevalence was assessed through macroscopic examination of the swim bladder, while traditional epidemiological metrics such as prevalence, mean intensity, and mean abundance were evaluated. Eels sampled in Lake Shkodra tested positive for A. crassus, with a prevalence rate of 36.9%. Younger individuals and males had the highest prevalence. At older ages, the intensity of the infection decreased. No infected eels were detected among the 156 specimens sampled in the Karavasta Lagoon. These results demonstrate habitat-specific variation in A. crassus infection and suggest environmental effects on parasite prevalence. The lack of infection in the Karavasta Lagoon questions its importance as a refuge for eels. More work is needed to investigate these ecological variations and their long-term effects on eel populations and conservation measures.

Keywords

European eel , Anguillicola crassus , swim bladder

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