Temporal variability of a temperate fish assemblage in Africa’s oldest marine protected area

Abstract

A standardised research-based, shore-angling survey was conducted in the 47-year-old Tsitsikamma National Park Marine Protected Area (MPA) between 1998 and 2005. The aim of this study was to examine variability in community structure, relative abundance (catch per unit effort, CPUE) and size frequency of the shore-angling fish assemblage in this no-take MPA. A total effort of 8 141 angler hours yielded 8 236 fish of at least 54 species from 19 families. The overall CPUE showed no significant trend over time (r² = 0.015, p = 0.1). The interannual variation in CPUE indicated relatively stable populations for some species (e.g. blacktail Diplodus capensis) and patterns of recruitment failure for others (e.g. galjoen Dichistius capensis). However, the lack of a significant trend in taxonomic distinctness (r² = 0.008, p = 0.8), the stable rank order of species abundance (χ², r = 361, p < 0.05) and the high coefficient of concordance (W = 0.84) indicated a relatively stable fish assemblage. This was attributed to the extended length of protection afforded by this MPA. One noticeable trend was an increase in the abundance of species with an affinity for warm water and whereas this correlated to an annual increase in water temperature of 0.024 °C between 1998 and 2005, a longer time-series is necessary to identify rise in sea temperature (climate change) as a driver of change in this warm-temperate fish assemblage.

Keywords: climate change, interannual variability, long-term monitoring, marine protected area, Tsitsikamma National Park

African Journal of Marine Science 2012, 34(1): 15–26