Knowl. Manag. Aquat. Ecosyst.
Number 424, 2023
Anthropogenic impact on freshwater habitats, communities and ecosystem functioning
|Number of page(s)||8|
|Published online||10 January 2023|
Effects of turbidity and introduced tilapia (Oreochromis spp) on macrophytes and invertebrates in a shallow tropical lake
Université de Toliara, École Doctorale de la Biodiversité et Environnements Tropicaux, BP304, Toliara 601, Madagascar
2 Wildfowl and Wetlands Trust, Antananarivo 101, Madagascar
3 Durrell Wildlife Conservation Trust, BP8511, Antananarivo 101, Madagascar
4 The Peregrine Fund, BP4113, Antananarivo 101, Madagascar
5 Wildfowl and Wetlands Trust, Slimbridge GL2 7BT, UK
* Corresponding author: firstname.lastname@example.org
Accepted: 1 December 2022
Tropical freshwater wetlands are subject to multiple stressors but there is little information on which stressors cause wetland degradation. Increased turbidity is considered a major cause of degradation, but the effects of introduced fish are often overlooked. Tilapia are frequently introduced in tropical regions, especially species in the genus Oreochromis, and the ecological effects of introducing tilapia are poorly studied. We used enclosure experiments in a shallow lake in Madagascar to assess the effects of tilapia and turbidity on macrophytes and benthic invertebrates, and to test management interventions designed to increase both. Tilapia at high and low stocking densities had negative effects on survival of Charophyte algae and water lilies, but no direct effect on benthic invertebrate abundance or diversity. Invertebrate abundance was highest on submerged Charophytes, so herbivory by tilapia indirectly affected invertebrates. Turbidity affected Charophyte survival, and abundance and diversity of non-Dipteran insects. As a complication, tilapia may increase turbidity by re-suspending the lake sediment. Our results suggest that herbivory by tilapia is a plausible cause of the removal of macrophytes from the lake and an impediment to their re-establishment. Tilapia are widely introduced in tropical areas as a food resource. Our results demonstrate serious consequences to these introductions.
Key words: Aquatic herbivory / submerged macrophyte / floating macrophyte / Cyperus papyrus
© L.A. Rasoamihaingo et al., Published by EDP Sciences 2023
This is an Open Access article distributed under the terms of the Creative Commons Attribution License CC-BY-ND (https://creativecommons.org/licenses/by-nd/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. If you remix, transform, or build upon the material, you may not distribute the modified material.
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