Huis River aquatic invertebrate survey strengthens partnerships for freshwater ecosystem conservation

In the upper reaches of the Huis River near Barrydale, a recent aquatic macroinvertebrate survey is helping to inform conservation decisions for the Critically Endangered Tradouw redfin (Pseudobarbus burchelli), including the potential expansion of its range into upstream habitats in the river. The survey was conducted in partnership with Grootvadersbos Conservancy and forms part of CapeNature’s ongoing efforts to support the conservation of the Tradouw redfin.

By examining aquatic macroinvertebrate communities in different reaches of the Huis River, including both fishless upstream sections and downstream reaches where redfin occur, the survey provides critical insight into ecosystem health and functioning. The information also forms part of a risk assessment for a potential conservation translocation for the redfin.

Using standardised SASS5 (South African Scoring System version 5) – a rapid biological monitoring method used to assess the ecological health of rivers in South Africa – four sites were assessed for water quality, habitat condition, and aquatic macroinvertebrate diversity. In addition to SASS, a complete invertebrate inventory was made for each site, and the invertebrates will be identified to species level by taxon experts at the Albany Museum. Based on SASS results, all sites were classified within a good to near-natural ecological condition. The upstream, fishless sections stood out for their high diversity and abundance of sensitive macroinvertebrate taxa, clear indicators of strong ecological integrity and relatively undisturbed habitat. The intact nature of these upstream systems not only supports diverse invertebrate communities, but also presents a potential opportunity for conservation interventions, including the expansion of redfin populations into suitable habitats.

Further downstream, while instream conditions remain good, slightly lower diversity and a greater presence of tolerant taxa reflect the influence of altered flow regimes (a result of water abstraction) and existing fish populations. This underscores the importance of maintaining environmental flows and habitat complexity to sustain ecosystem function. Importantly, the survey establishes a scientific baseline for ongoing monitoring and adaptive management. CapeNature continues to implement evidence-based conservation strategies, and this work highlights the role of research and partnerships in safeguarding freshwater ecosystems for the future.