1. Crayfish are invasive polytrophic keystone species, which are phylogenetically unique on the African continent. The Australian redclaw crayfish Cherax quadricarinatus is invasive in southern African freshwater systems including the Zambezi River Basin. Surveys conducted across the Zambezi Basin (Botswana, Zimbabwe, Namibia and Zambia) between 2017 and 2019 showed that C. quadricarinatus is broadly distributed across the Upper and Middle Zambezi and is rapidly spreading through natural and human-mediated means across several ecoregions.
2. The probability of capture (P_capture), catch per unit effort (CPUE) and population characteristics of C. quadricarinatus from the recent Barotse floodplain invasion were compared with older invasions from Lake Kariba and Kafue River.
3. The P_capture and CPUE of C. quadricarinatus in the recently invaded region of the Barotse floodplain were similar to those of the older invasions. Mass and carapace length of C. quadricarinatus from the Barotse floodplain were significantly lower than those of C. quadricarinatus from the older invasions. Sex ratios differed significantly between the three invasive populations. The Barotse floodplain population had a disproportionate investment in females (65.3%) and intersex individuals (8.4%). No crayfish were detected in the Zambezian Headwaters or the Okavango Floodplains ecoregions, but current spread rates are 49 km yr⁻¹ downstream and 12 km yr⁻¹ upstream.
4. Investment in population management and the prevention of spread will have high conservation value across the invaded regions in order to restrict crayfish ecological impacts via direct predation and competition. In areas where crayfish are in high abundance, existing fisheries are affected through damage to nets, leading to increased net abandonment and ghost gear pollution in invaded regions.
5. The emphasis should be on developing cohesive transboundary biosecurity policies in southern Africa to limit further spread that will threaten the integrity of freshwater ecosystems. However, long-term monitoring is needed to gauge invasion risk to sensitive areas such as the Okavango Floodplains ecoregion and determine field-based ecological impacts.

中文翻译：

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外来澳大利亚红爪小龙虾Cherax quadricarinatus在赞比西河流域的分布与定殖

1. 小龙虾是入侵性多营养关键物种，在非洲大陆的系统发育上是独一无二的。澳大利亚红爪小龙虾Cherax quadricarinatus是非洲南部淡水系统的入侵物种，包括赞比西河流域。2017 年至 2019 年期间在赞比西河流域（博茨瓦纳、津巴布韦、纳米比亚和赞比亚）进行的调查表明，C. quadricarinatus广泛分布在赞比西河上游和中部，并通过自然和人类介导的方式迅速传播到多个生态区。
2. 将近期 Barotse 洪泛区入侵的C. quadricarinatus的捕获概率 ( P _capture )、单位努力捕获量 (CPUE) 和种群特征与来自卡里巴湖和卡富埃河的较早入侵进行了比较。
3. 最近入侵的 Barotse 洪泛区的C. quadricarinatus的P_捕获和 CPUE与较旧的入侵相似。来自 Barotse 洪泛区的C. quadricarinatus 的质量和甲壳长度显着低于来自较旧入侵的C. quadricarinatus。三个入侵种群之间的性别比例存在显着差异。Barotse 洪泛区人口对女性 (65.3%) 和双性人 (8.4%) 的投资不成比例。在赞比西河源头或奥卡万戈洪泛区生态区未检测到小龙虾，但目前的传播速度为下游49 公里 yr ^-1和上游12 公里 yr ^-1。
4. 通过直接捕食和竞争来限制小龙虾生态影响，投资于种群管理和防止传播将在入侵地区具有很高的保护价值。在小龙虾丰度高的地区，现有渔业因渔网损坏而受到影响，导致被入侵地区的渔网遗弃和幽灵渔具污染增加。
5. 重点应该是在南部非洲制定有凝聚力的跨界生物安全政策，以限制将威胁淡水生态系统完整性的进一步蔓延。然而，需要长期监测来衡量对奥卡万戈洪泛区等敏感地区的入侵风险，并确定实地生态影响。