Patterns in reef fish assemblages as determined by baited remote underwater video (BRUV) along the western side of False Bay: effects of site, depth and protection status

Master Thesis


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University of Cape Town

By protecting ecosystems from exploitation, no-take zones are considered the principal means by which marine species and their populations can be conserved for future generations. To be successful, no-take zones require continuous monitoring of the fish community to evaluate the response of marine ecosystems to anthropogenic impacts and environmental change. Obtaining an understanding of the patterns of species composition, abundance, and distribution, allows monitoring efforts to be focused, efficient, and properly interpreted. Baited remote underwater video (BRUV) was used to examine the effects of site, depth, andlevel of protection, on the diversity and relative abundance of temperate reef fish within the Table Mountain National Park (TMNP) Marine Protected Area (MPA). Four notake zones and adjacent exploited areas, subject to conventional management restrictions, were sampled monthly over a four-month period. A total of 36 species from three marine classes and 18 families was recorded. Species diversity (Shannon-Wiener index) was found to increase with sites closest to the mouth of the bay, whilst species abundance was found to increase with depth. Results indicated no consistent response to protection status among the sites at either the community or individual species level. However, the oldest no-take zone proclaimed for the purposes of reef conservation was found to harbour higher species diversity and a higher relative abundance of fish compared to its respective exploited area. Furthermore, the similar frequencies in which hottentot (Pachymetopon blochii) and roman (Chrysoblephus laticeps) were observed across the four study sites, suggests that these two commercially-important species are successfully recruiting inside and outside the no-take zones. These results indicate that physical factors, rather than protection status, within False Bay influence patterns of fish assemblage composition, abundance, and distribution. In future, and to improve comparability, assessments within the TMNP MPA should be designed to target similar locations and depth ranges within the bay. The success of no-take zones must be evaluated according to their individual design and management goals.

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