Marine mussel beds as attractive habitats for juvenile European eel (Anguilla anguill); A study of bottom habitat and cavity size preferences

A substantial part of the European eel population never enters freshwater. To include the marine areas in eel management, knowledge about their marine habitat selection is needed. The present study describes the burial behavior of elvers and their substrate preferences by types and burial cavity sizes. In one experiment, the selective behavior of elvers between four different marine substrata: blue mussels, large gravel, small gravel and sand were investigated. In a second experiment we examined the selective behavior of elvers, when offered shelter in artificial cavities as tubes of five different diameters. The results showed clear elver preference for the mussel substrate, the habitat with the largest cavities, less preferred were large and small sized gravel while the sand substrate was avoided. When offered shelter in tubes of different diameters, the elvers did not use the largest, but preferred shelter in the smaller tubes, which is equivalent to the smallest cavity sizes observed in the mussel and large gravel substrates. The findings point to structured habitats, such as blue mussels and large gravel of intermediate cavity sizes, as important habitats to elvers. The presence of such shelters should be considered when planning future management initiatives and restoration projects.