Baetid abundances are a rapid indicator of thermal stress and riparian zone intactness.

Riparian zone vegetation plays an integral role in freshwater ecology, notably by buffering water temperatures, and in providing habitat for the adult stages of many aquatic species. We measured the contribution that riparian vegetation makes to temperature buffering, and how this affects the freshwater fauna, specifically using changes in abundances of baetid may flies for the Luvuvhu River catchment in South Africa. Water temperatures were compared for shaded versus un-shaded sites, and thermal stress between seasons was estimated using a cumulative probability model for the most widespread mayfly species, Dabulamanzia media. It is concluded that thermal stress due to losses in riparian shading could be detected using mayfly abundances in a regular monitoring programme.

Evaluation of larvicides in developing management guidelines for long-term control of pest blackflies (Diptera: Simuliidae) along the Orange River, South Africa.

In 2000 and 2001 Orange River levels were higher than normal: associated serious outbreaks of blackfly had a substantial detrimental impact on the local economy. The poor control was attributed to the suspected development of larval resistance to temephos. A long-term solution to blackfly control, through the identification of a suitable replacement to temephos for use during high flow conditions, was proposed. This study, however, failed to identify or register a suitable larvicide for use during high flow conditions. Although permethrin was highly effective against blackfly larvae, it was rejected because of its detrimental impacts on non-target fauna. Various formulations of locally produced dry Bacillus thuringiensis var. israelensis (B.t.i.) were tested, but these were ineffective against blackflies. The study also confirmed that resistance to temephos has developed among Simulium chutteri in the middle and lower Orange River. The feasibility of "reversing" the resistance to temephos through the use of the synergist piperonyl butoxide (PBO) was investigated, but the results were not favourable. Furthermore, PBO was highly toxic to blackflies and non-target organisms, and was not recommended for further testing. This means that B.t.i. currently remains the only symptomatic measure of treatment currently applied. Although resistance to B.t.i. has not been reported for blackflies elsewhere in South Africa, there is a need to remain vigilant and to implement an operational strategy that minimizes the risks of resistance developing.

Adaptive management and water temperature variability within a South African river system: what are the management options?

Water temperatures, and in particular daily maximum water temperatures, are a critical water quality parameter. An understanding of associated resource management issues, including links between water temperature variability and aquatic diversity values, should be part of any management programme that considers river systems. Simple rule-based models have been shown to be appropriate tools within an adaptive management approach, both because of their heuristic value and in their application for scenario generation. Such a model was developed to simulate changes in the condition factor of Chiloglanis anoterus [Crass, R.S., 1960. Notes on the freshwater fishes of Natal with descriptions of 4 new species. Annals of the Natal Museum 14, 405-458] (Pisces: Mochokidae) in response to annual frequency of exceedance of a threshold temperature under three broad environmental scenarios for part of the Sabie River falling within South Africa's Kruger National Park. This model has potential for application within the adaptive management programme being implemented by the Kruger National Park. Results show that under broad scenarios of a 10% reduction in mean daily flow rates, or a 2 degrees C increase in mean daily air temperatures, system variability is likely to increase relative to reference conditions . It is suggested that so-called "thresholds of probable concern" (TPCs), which are based on current levels of "natural" system variability, are useful as management targets for achieving a "desired future state" for the river system. The model, recognised as a preliminary hypothesis, highlights a lack of knowledge regarding the nature of system variability, and the correspondingly wide confidence limits of the proposed TPC restricts its utility in a short-term management context. Thus, it is now recognised that its value lies more in its use as a long-term modelling tool to reflect water temperature responses to flow variability. This highlights the fact that research outcomes may not always be those intended at the beginning of a project and that opportunities to implement these may be lost as lags in understanding relative to project lifetimes often exist.