Freshwater fish richness baseline from the São Francisco Interbasin Water Transfer Project in the Brazilian Semiarid

Abstract Among Neotropical freshwater ecoregions, the Mid-Northeastern Caatinga (MNCE) is a fish knowledge gap. Its temporary drainages are receptors of the São Francisco interbasin water transfer project (SFR-IWT) in the Brazilian semiarid. We provide a comprehensive baseline of fish richness of the five SFR-IWT basins. Species richness, shared, endemic, threatened and non-native species were obtained using sampling, ichthyologic collections, literature and online repositories (306 localities). In total 121, species were recorded, 111 of them native, and 16 (14.41%) listed for all basins. Higher richness of native species (78, 70.27%) was recorded in the São Francisco lower-middle stretch (SFRE), including 23 endemic, 61 (54.95%) in MNCE basins (13 endemic), and 28 (25.23%) shared between both ecoregions. In the MNCE, 50 species were recorded in Jaguaribe (JAG), 39 in Piranhas-Açu, 36 in Paraíba do Norte, and 32 in Apodi-Mossoró (APO). The number of species shared between the SFRE and each receptor basin varied from 24 (23.08%, JAG) to 20 (22.22%, APO). JAG contains 81.97% of the receptor basins’ species. Its higher richness and endemism deserve special attention regarding the ongoing hydrological changes. This study will help detect possible modifications in the ichthyofauna of the main MNCE drainages.

摘要 在新热带淡水生态区（Neotropical freshwater ecoregions）中，中东北部卡廷加（Mid-Northeastern Caatinga, MNCE）是鱼类研究的空白区域。该区域的季节性径流河道为巴西半干旱地区的圣弗朗西斯科跨流域调水工程（São Francisco interbasin water transfer project, SFR-IWT）的受纳水体。本研究针对SFR-IWT涉及的5个流域，构建了鱼类物种丰富度的综合基线数据。研究通过野外采样、鱼类馆藏标本查阅、文献调研及在线数据库检索（覆盖306个采样点），获取了各流域的物种丰富度、共有物种、特有物种、受威胁物种及外来物种数据。本研究共记录鱼类121种，其中本土物种111种，另有16种（占比14.41%）在全部5个研究流域均有分布。圣弗朗西斯科河中下游流域（SFRE）的本土物种丰富度最高，计78种，占本土物种总数的70.27%，其中包含23种特有种；中东北部卡廷加流域（MNCE）的本土物种丰富度为61种，占比54.95%，含13种特有种；两个生态区共有物种28种，占比25.23%。在MNCE范围内，Jaguaribe（JAG）流域记录到鱼类50种，Piranhas-Açu流域39种，Paraíba do Norte流域36种，Apodi-Mossoró（APO）流域32种。SFRE与各受纳流域的共有物种数量介于20至24种之间：其中JAG流域与SFRE的共有物种为24种，占该流域物种总数的23.08%；APO流域为20种，占比22.22%。JAG流域的物种数占MNCE所有受纳流域物种总数的81.97%。鉴于当前持续发生的水文变化，JAG流域较高的物种丰富度与特有物种占比值得重点关注。本研究可为监测MNCE主要径流河道的鱼类区系变化提供科学支撑。