The impacts of grazing by tilapias Oreochromis / niloticus L. on periphyton communities growing on artificial substrate in cages
نویسندگان
چکیده
This study describes the development of periphytic communities established on artificial Ž . substrates in tilapia Oreochromis niloticus cages during a 10-week experiment conducted in the Meghna River, Bangladesh. Qualitative and quantitative characteristics of the periphyton were recorded, including diatom community composition and primary productivity. Fish grazed actively on the periphyton and there was a rapid fall in periphyton biomass following their introduction to Ž . the cages. Grazing significantly P-0.05 affected the horizontal and vertical periphyton biomass distribution over time. Tilapia showed only limited feeding selectivity, both animal and plant material being removed to an equal extent, although there was less ingestion of smaller particles. Ž . Fish grazing significantly P-0.05 reduced diatom diversity, mean diatom biovolume, the variability in standing periphyton biomass and the proportion of ash. Grazed periphyton communities were younger, healthier and more productive. The significance of these findings for caged production of fish are discussed. q 2000 Elsevier Science B.V. All rights reserved.
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