Movement and habitat use of native and non-native small benthic fish in a high conservation value agricultural environment

Despite the considerable progress that has been made in the field of taxonomy and genetics of freshwater fish, there is still a paucity of knowledge regarding their ecology and behaviour. We used PIT-telemetry to study movement and habitat use of native and non-native benthic fish species in a spring-fed irrigation stream, subject to seasonal macrophyte removal, in a rice field in North-Western Italy. This anthropogenically managed environment constitutes a habitat of high conservation value for some important endemisms, while hosting several non-native species. Fish were tracked both using manual tracking and stationary PIT-antennas, and telemetry data was complemented with catch data from electrofishing. The native P. bonelli and the non-native M. anguillicaudatus were tracked in sufficient numbers to allow quantitative analysis. While successfully tracked in the study area, both species were mostly stationary, but some fish registered movements in the study area of several hundred meters. M. anguillicaudatus showed a tendency of greater movements. With time, most fish disappeared from the study area but no direct migratory movement was detected. M. anguillicaudatus showed a clear preference for macrophyte-covered substrates while P. bonelli were frequently tracked both among macrophytes and on gravel substrates. Electrofishing data showed higher fish abundance in reaches subject to only partial macrophyte removal (fish-friendly management) compared to those subject to standard removal. Overall, movement seems to be an integral part of the ecology of benthic fish in this system, where vegetation appears to structure their spatial behavior.