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

Abstract

Abstract Since most of the natural habitats critical for freshwater fish survival have been adversely affected by human disturbance, the effectiveness of artificial structures in providing new and suitable habitats for fish has been increasingly investigated. This paper evaluates the role of artificial structures as fish habitat in a structureless 30 km2 Brazilian reservoir, through underwater surveys conducted monthly from April 1999 to March 2000. In total, 5759 fish in 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. The absence of fish at control sites compared with high occurrences in sites provided with a physically complex structure suggests that artificial structures can play an important ecological role for cichlids smaller than 150 mm TL, probably related to shelter and/or feeding benefits. The level of structural complexity and position in the water column influenced fish use of artificial structures. C. kelberi was associated with highly complex structures, whereas moderately complex bottom structures were more effective in harbouring G. brasiliensis. Bottom structures are apparently more important than midwater structures in harbouring T. rendalli, but structural complexity seemed to play a secondary role. This study is the first in demonstrating that adding complex artificial structures can expand habitats for small fish (<150 mm TL), especially cichlids, in a neotropical impoundment. It seems reasonable to expect that deploying physically complex structures in other oligotrophic, structureless and cichlid‐dominated impoundments in Brazil will lead to similar results to those found in this work. Copyright © 2008 John Wiley & Sons, Ltd.