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Diseases of Aquatic Organisms

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DAO 155:21-33 (2023)  -  DOI: https://doi.org/10.3354/dao03739

Infection with swim bladder nematode Anguillicola crassus in relation to European eel growth, age, and habitat along the German Baltic coast

Janek Simon1,*, Claus Ubl2, Wolf-Christian Lewin3, Malte Dorow2

1Potsdam Institute of Inland Fisheries, Im Königswald 2, 14469 Potsdam, Germany
2Institute for Fisheries, Mecklenburg-Vorpommern State Research Centre for Agriculture and Fisheries, Fischerweg 408, 18069 Rostock, Germany
3Thünen Institute of Baltic Sea Fisheries, Alter Hafen Süd 2, 18069 Rostock, Germany
*Corresponding author:

ABSTRACT: One possible reason for the European eel (Anguilla anguilla) population decline is the neozoan eel swim bladder nematode Anguillicola crassus. To investigate whether the prevalence of A. crassus and the associated swim bladder pathology is related to eel habitat, growth rate, and age, 728 yellow eels from 6 habitats differing in salinity and located along the German Baltic coast were examined between 2005 and 2009. The prevalence of A. crassus varied between habitats, ranging from 9 to 57%. Infection prevalence and the percentage of eels with a damaged swim bladder were significantly higher in inner coastal waters compared to more saline open coastal water. In infected eels, 1 to 32 adult and preadult individuals of A. crassus were observed. The mean infection intensity varied between habitats from 2 to 7 nematodes per eel but did not significantly differ between inner and open coastal waters. Infection prevalence and intensity decreased significantly with age when all open coastal waters and all habitats were combined. Both the lower prevalence of A. crassus and the swim bladder damage of older eels and of eels originating from open coastal water habitats suggest that these eels have a higher fitness for spawning migrations than eels from inner coastal waters. The present study underlines the importance of eel screening on a sufficiently small geographical scale for the accurate estimation of eel recruitment and the identification of priority areas that are likely to produce healthy silver eels.


KEY WORDS: Anguilla anguilla · Neozoan · Nematode · Parasitism · Salinity · Baltic Sea


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Cite this article as: Simon J, Ubl C, Lewin WC, Dorow M (2023) Infection with swim bladder nematode Anguillicola crassus in relation to European eel growth, age, and habitat along the German Baltic coast. Dis Aquat Org 155:21-33. https://doi.org/10.3354/dao03739

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