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Long-term monitoring of subtidal reef fishes in the Tsitsikamma Marine Protected Area
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By Denham Parker, Department of Ichthyology and Fisheries Science, Rhodes University and Albrecht Götz, SAEON
Tsitsikamma is the oldest - and one of the largest (320km2) - ‘no-take’ Marine Protected Areas in Africa.
After 40 years of protection, the marine communities here are stable and provide the best example of pre-exploitation inshore ecosystems available today.
In July 2012, SAEON’s Elwandle Node conducted the twelfth trip for the monitoring of subtidal reef fishes in the Tsitsikamma Marine Protected Area (MPA). The project is in its sixth year, with biannual sampling trips in summer and winter.
This research project uses standardised bait angling methods to sample fish communities in the nearshore reef ecosystems. To date, more than 200 fishing stations have been completed, and a total of 2,257 fish belonging to 43 different species have been caught and released.
This dataset already represents the longest and most comprehensive subtidal reef fish abundance estimate in southern Africa.
Assessing climate change impacts
Recently a PhD student, Denham Parker, joined SAEON to assess the possible impacts that climate change may have on the relatively fragile subtidal reef fish communities in the Tsitsikamma MPA.
Climate change is undeniably regarded as the largest environmental predicament faced by humans, yet the science needed for global-scale ecological understanding is immature and thus the magnitude and extent of effects remain largely unknown. This is further hindered by a lack of long-term ecological data, as the timescales of research projects are generally minute when compared to that of global climatic events.
In an attempt to overcome these limitations, SAEON’s Elwandle Node is exploring more feasible methods of assessing the possible impacts of climate change on fish communities. These include the use of isolated sporadic climatic events which are linked to long-term climate change such as El Niño and La Niña. These events are well recorded globally, and in situ temperature loggers have provided records of significant deviations from ‘typical’ water temperatures in Tsitsikamma during such events.
These abnormal fluctuations have been shown to impose changes in fish species and size compositions, abundance and recruitment ability. It is thought that these types of sporadic climatic events will intensify and become more frequent as the global climate continues to change.
Tsitsikamma is relatively pristine and situated in the centre of the warm-temperate biogeographic region. As such, it is thought that the underlying mechanisms that drive natural variability and climate change effects on fish resources can be described, mathematically modelled and generalised over larger geographic scales. Essentially this means that superimposed anthropogenic influences can be separated from natural drivers.
Convincing early-warning system
This will result in realistic ecosystem trends which can be used to equip decision makers with a convincing early-warning system for conservation and fisheries management. These types of predictive models will allow managers to implement the best possible practices to mitigate the negative effects of climate change and minimise human induced ecological degradation.
Adaptation of fisheries and fisheries management to a changing environment is imperative when nearly 1.5 billion people rely on fish for more than 20 per cent of their protein.
