Experimentally increased turbidity causes behavioural shifts in Lake Malawi cichlids

The aquatic environment is being perturbed globally through increases in turbidity, which can have detrimental effects for the maintenance of fish diversity, especially in species dependent on visual cues for reproduction and species recognition. We performed a short-term manipulation of the visual environment in Lake Malawi to test for an immediate behavioural response to increased turbidity in territorial rock-dwelling cichlid fishes that use colourful visual cues to maintain territories near the substrate and attract mates. We found a significant movement of fish away from the substrate, with a concomitant shift from displaying territorial and courting behaviours to foraging behaviours, during the five minutes following the release of a turbidity plume over the area. This study is the first to test for and demonstrate an immediate behavioural response of a natural fish population to a short-term increase in turbidity that might mimic the initial (i.e., immediate) stage of a run-off event after rainfall in a deforested area.