Artificial structures as tools for fish habitat rehabilitation in a neotropical reservoir

1. Since most of the natural habitats critical for freshwater fish survival have been adversely affected by human disturbance, the effectiveness of artificial structures ill providing new and suitable habitats for fish has been increasingly investigated. 2. This paper evaluates the role of artificial structures as fish habitat ill a structureless 30 km(2) Brazilian reservoir, through underwater surveys conducted monthly from April 1999 to March 2000. 3. In total, 5759 fish ill nine species were recorded. but only three cichlid species-one native, Geophagus brasiliensis and two non-native, Cichla kelberi and Tilapia rendalli-showed consistent association with the artificial habitats. suggesting that this family reacts to submerged structures. 4 The absence of fish at control sites compared with high occurrences ill sites provided with a physically complex structure suggests that artificial structures can play all important ecological role for cichlids smaller than 150mm TL, probably related to shelter and/or feeding benefits. 5. The level of structural complexity mid position ill the water column influenced fish use of artificial structures. C. Kelberi was associated with highly complex sturctures, whereas moderately complex bottom structures were more effective ill harbouring G. brasiliensis. Bottom structures are apparently more important than midwater structures ill harbouring T. rendalli. but structural complexity seemed to play a secondary role. 6. This study is the first ill demonstrating that adding complex artificial structures Call expand habitats for small fish ( < 150 mm TL). especially cichlids, ill a neotropical impoundment. It seems reasonable to expect that deploying physically complex sturctures ill other oligotrophic. sturctureless and cichlid impoundments in Brazil will lead to similar results to those found in this work. Copyright (C) 2008 John Wiley & Sons, Ltd.