Distribution and community structure of Chaetodontidae (Perciformes) in iSimangaliso Wetland Park with the view to applying the Butterflyfish Indicator Hypothesis in this region of South Africa

Bachelor Thesis


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University of Cape Town

Coral reefs are globally in a vulnerable state, because of both human impacts and environmental alterations. An understanding of coral reef ecosystems and the ability to detect changes in the reef environment early on are necessary to apply effective conservation. The co-evolution of coral and coral feeding fishes means that some species may exhibit interactions useful for indicating reef health, acting as an early warning system. Chaetodontidae (Perciformes) are one such family, containing coral dependent (obligate corallivore) species. This concept is known as the Butterflyfish Indicator Hypothesis (BIH). Through the collection of baseline data for butterflyfish abundance, diversity and species composition, the possible applicability of the BIH was investigated within Marine Protected Areas (MPA¡¯s) of iSimangaliso Wetland Park, on the north-eastern coast of South Africa. Other factors possibly impacting butterflyfish distribution were also investigated in this region. These factors were level of MPA protection (sanctuary or partially protected), reef rugosity and site effects. 78 transects across 13 dive sites were swum using Underwater Video Census (UVC) for data capture. Reef rugosity displayed no impact on any of the sampled factors, whilst site and protection level did. Protection was the factor with the greatest influence on butterflyfish species richness (df = 77, t = 2.85, p < 0.005), evenness of spread (df = 77, t = 1.79, p < 0.05) and total abundance, as revealed by the General Linear Model (GLM) with the lowest Aikake¡¯s Information Criterion (AIC) (y = ¥â&#8338; + ¥â©û (protection)). None of the factors altered Chaetodon meyeri distribution significantly, the only observed obligate corallivore, for which low abundances were observed. Differences in total butterflyfish abundance and species diversity appear to be particularly useful in revealing human impacts on coral health. The lack of C. meyeri, likely accounted to low abundances of its preferred coral Acropora (Scleractinia: Acroporidae), suggest that the BIH is not useful in this region.

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