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Since 2012, several organisations have been monitoring the Tradouw redfin Pseudobarbus burchelli population and the overall health of the Huis and Tradouw river systems. From 2018 onwards, the Grootvadersbosch Conservancy (GVB) has played a leading role through various freshwater conservation initiatives—most notably the Grootvadersbosch Aquatic Species Protection Project (GASPP), implemented in partnership with CapeNature and funded by the Table Mountain Fund. Although GASPP concluded in 2022, one of its key achievements was the development of local knowledge and capacity for long-term monitoring. GVBC has since continued annual monitoring in April/May and October/November across 59 sites between Riversdale and Swellendam.  A Tradouw Redfin being measured before returning it to the Huis River GVBC recently hosted a workshop focused on developing a species action plan—funded by the IUCN Species Survival Commission—which will inform the drafting of a Biodiversity Management Plan (BMP) for the Barrydale redfin. Once this BMP is approved, the Minister of Environment will appoint a lead agency and publish the plan in the Government Gazette. The BMP then becomes binding, providing additional legal protection for the species. Furthermore, the publication of a BMP and the signing of a Biodiversity Management Agreement between qualifying taxpayers and the Minister may unlock a tax incentive. This incentive allows for the deduction of qualifying conservation and maintenance expenses from taxable income—effectively reducing tax liability and encouraging conservation efforts.  Dr Jordaan discusses the concerning trends in the population numbers of the Tradouw redfin During our first workshop in March, Dr Martine Jordaan from Cape Nature commented on a noticeable decline in redfin numbers in the Tradouw Pass and emphasised the need for more intensive sampling to confirm these trends. In response, a comprehensive fish monitoring survey was conducted by GVBC over a 7 km stretch of the Tradouw Pass, in collaboration with the Gouritz Cluster Biosphere Reserve. This took place in April 2025—our usual monitoring period—but involved a more extensive effort, using eight nets across five sites (as opposed to the usual one or two nets at one site). The results were concerning- not a single redfin was recorded across all the sites. This represents a significant decline when compared with past surveys and points to increasing pressure on this river system. Historically, eels have also been found in the system, but none were detected in the recent survey, despite. Surprisingly, very few invasive fish were found either—just two juvenile tilapia at one site. These findings raise critical questions about the river’s current ecological state. What could be occurring downstream that is preventing eel migration? And what’s driving the decline in redfin populations in the Tradouw Pass? Could it be linked to a recent flood event or sudden changes in water temperature? These are pressing questions that require further investigation and ongoing monitoring. These results are consistent with Dr Jordaan’s observations over the past decade: a steady decline in the redfin population, particularly in the Tradouw system. This highlights the increasing importance of the Huis River system for the species' survival and underscores the need for a robust management plan to ensure the survival of the species. On a more positive note, the species has officially been named as Pseudobarbus burchelli (common name Tradouw redfin) and the details are updated in the new Field Guide to the Freshwater Fishes of Southern Africa (Skelton, 2024). This formal recognition strengthens the case for its conservation and brings renewed attention to the urgent need for action.  Longfin eels (Anguila mossambica) are often found in the Tradouw pass but were not observered in the most recent samplying
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In the biodiverse landscapes of the Western Cape, a quiet but critical battle is underway. Invasive alien plants are spreading rapidly, crowding out native fynbos, stealing water from already-stressed ecosystems, and increasing the risk of destructive wildfires. Invaders like Port Jackson willow (Acacia saligna), hakea (Hakea sericea), black wattle (Acacia mearnsii) and lantana (Lantana camara) are not only difficult to control—they are deeply harmful to South Africa’s ecosystems. They displace native species, reduce biodiversity, and degrade both soil and water resources. To win this battle, we need every tool at our disposal. At the Grootvadersbosch Conservancy (GVBC), we’re working with partners to combine mechanical and chemical control methods with innovative, nature-based solutions—specifically, biological control. GVBC is collaborating with leading researchers from institutions such as the Agricultural Research Council (ARC), the Centre for Biological Control at Rhodes University, and the University of Cape Town to promote and distribute biological control agents—specialist insects and mites that target invasive plants without harming native species. These tiny organisms are highly specific to their host plants, making them powerful allies in long-term ecological restoration. By harnessing their natural behaviours, biocontrol transforms scientific research into tangible on-the-ground results. Meet some of the heros
Each of these agents plays a targeted role in weakening invasive plant populations and helping restore the balance of native ecosystems. Learn More About Other Biocontrol Agents GVBC recently hosted a training workshop with Dr Fiona Impson, where she introduced the key biological control agents used in the Western Cape and demonstrated how to help capture and distribute them. You can watch the training on our YouTube channel. The Growing Threat of New Invasive Plants: Lantana camaraLantana camara is emerging as a significant threat in our area. This thorny, fast-growing shrub forms dense thickets that shade out indigenous plants and block wildlife movement. It’s toxic to some livestock and wildlife, and its colourful berries allow it to spread rapidly via birds and mammals. Manual removal is extremely labour-intensive, and chemical treatment is both costly and unsustainable. While lantana was historically more common in the eastern parts of the country, it is now spreading rapidly in the Western Cape—possibly due to shifting climate and weather patterns. With the help of Dr Fiona Impson and Dr Alan Wood, GVBC recently released a biological control agent to combat this tough invader. Aceria lantana: A Microscopic Marvel Aceria lantana is a species of gall-forming mite, carefully selected and tested by biocontrol scientists to specifically target Lantana camara. These mites are host-specific, meaning they pose no threat to other plants, animals, or people. Once introduced into the environment, they settle on the leaves and stems of lantana plants and begin feeding. What makes them especially effective is their ability to disrupt plant growth. As they feed, the mites induce the formation of tiny galls—swollen, abnormal tissues—that interfere with nutrient flow, inhibit flowering, and reduce the plant’s ability to reproduce and spread. Over time, repeated mite activity leads to a noticeable decline in lantana’s density and vigour. GVBC recently released Aceria lantana in a test area. Unfortunately initial results do not look as effective as hoped but more releases are planned to increase the potentail impact and spread. 
How You Can Help Biocontrol is a powerful conservation tool—but it’s even more effective with community support. Here’s how you can get involved:
GVBC’s work is driven by partnerships and community action. Learn more about biocontrol, support ongoing research, or get involved by visiting the GVBC website. Together with ARC, Rhodes University, and a network of passionate conservationists, we’re showing that sometimes the smallest heroes can make the biggest impact.  |
AuthorGVB Conservancy Staff Archives
June 2025
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