The Cape Fold Ecoregion (CFE) is one of southern Africa’s unique aquatic ecoregions and its freshwater fish fauna is characterized by high levels of endemism. As with many other Mediterranean-type ecosystems, the region is also a hotspot for threatened and range-restricted freshwater fish. Many of the CFE’s endemic species are at risk for extinction, with declines in population sizes and distribution ranges. The Clanwilliam sandfish Labeo seeberi is an example of such a species and is considered one of South Africa’s most endangered large migratory cyprinids. This species is endemic to the Olifants/Doring river system in the CFE and has been subject to a major population decline, mainly as a result of invasive alien fish and adverse climate events. Little is known of the genetics of the Clanwilliam sandfish, thus this study aimed to provide basic population genetic parameters to inform future conservation interventions. Both microsatellite and mitochondrial DNA (mtDNA) markers were used to assess populations from three sites within the Olifants/Doring river system. Genetic diversity was moderate to low and did not reflect the drastic decline expected on the basis of previous relative abundance data. This is likely due to a lag effect between ecological/life history demographics (due to juvenile recruitment failures) and population genetic composition. Furthermore, there was limited genetic differentiation between the sampling locations, suggesting a single breeding population, but mtDNA haplotype distribution and slight divergence of the smaller populations does suggest that the population might have become recently fragmented. The results show that the effective population size of the current breeding population might still be sufficient to maintain evolutionary potential in the short term, which could act as a buffer until conservation strategies focusing on protecting breeding animals and maximizing juvenile survival can restore population numbers.

开普褶皱生态区 (CFE) 是南部非洲独特的水生生态区之一，其淡水鱼类区系具有高度特有性的特点。与许多其他地中海型生态系统一样，该地区也是受威胁和范围受限的淡水鱼的热点地区。随着种群规模和分布范围的减少，许多 CFE 特有物种面临灭绝的危险。Clanwilliam 沙鱼Labeo seeberi就是此类物种的一个例子，被认为是南非最濒危的大型洄游鲤鱼之一。该物种是 CFE Olifants/Doring 河流系统的特有物种，由于外来鱼类入侵和不利的气候事件，其种群数量大幅下降。人们对克兰威廉沙鱼的遗传学知之甚少，因此本研究旨在提供基本的种群遗传参数，为未来的保护干预措施提供信息。微卫星和线粒体 DNA (mtDNA) 标记均用于评估 Olifants/Doring 河流系统内三个地点的种群数量。遗传多样性为中度至低度，并未反映出根据先前相对丰度数据预期的急剧下降。这可能是由于生态/生活史人口统计（由于幼体招募失败）和种群遗传组成之间的滞后效应。此外，采样地点之间的遗传分化有限，表明存在单一繁殖群体，但 mtDNA 单倍型分布和较小群体的轻微分歧确实表明该群体最近可能变得支离破碎。结果表明，当前繁殖种群的有效种群规模可能仍足以在短期内维持进化潜力，这可以起到缓冲作用，直到以保护繁殖动物和最大化幼体生存为重点的保护策略可以恢复种群数量。