Diet and condition of three fish species (Characidae) of the Andean foothills in relation to deforestation.

Bojsen, Berit

I studied effects of deforestation on diet and condition of three characid species;Astyanax zonatus,Knodus gamma, andPrionobrama filigerain small streams in the Ecuadorian Amazon. The best condition ofK. gammawas found at sites with low canopy cover, while the best condition ofP. filigerawas found at sites with high canopy cover. Deforestation changed population structure ofA. zonatusby decreasing mean size of individuals, but this was not associated with lower fish condition.A. zonatuswas omnivorous, and fed equally on invertebrate and plant food.A. zonatusincreased feeding on aquatic food items (filamentous algae and fish scales) in the deforested sites (43%) compared to the forested sites (16%).K. gammawas an omnivorous species with preference for invertebrates.K. gammawas mainly feeding on terrestrial food sources in the forested sites, but switched to equal feeding between terrestrial and aquatic food sources in the deforested sites.P. filigerawas an terrestrial insectivore feeder, and no differences in the overall food categories was found between stream groups. In contrast, there were no pronounced difference in the composition of invertebrate taxa in the stomachs ofK. gammabetween stream groups. However, less empty stomachs were observed amongK. gammain the deforested sites. The stomach contents ofP. filigerashowed great changes in composition of the predominating prey taxa between stream groups and less empty stomachs were observed amongP. filigerain the forested sites. Food availability and utilisation seemed to be of main importance for the condition of these fish. Deforestation seems to favour species with high availability to utilise aquatic food items. In contrast, deforestation seems to have negative effects on species that are specialised on terrestrial invertebrates, and have low capacity to switch between aquatic and terrestrial food items.

AMAZON River Region; ECUADOR; ASTYANAX; CHARACIDAE; AQUATIC resources; FISH food; FISH behavior

Environmental Biology of Fishes, 2005, Vol 73, Issue 1, p61

0378-1909

Academic Journal

10.1007/s10641-004-5330-y