Under the surface: what we know about the threats to subterranean fishes in Brazil

Abstract The present work brings information on threats to the subterranean fishes in Brazil. Currently, at least 36 species are known, 22 of which are already formally described. Endemism is the rule for most of them. Regarding their conservation, these fishes are in general considered threatened: and most of the already formally described species are included in national lists of threatened fauna, and only four of them are included in the global list of the IUCN. Regarding habitats, Brazilian subterranean fishes occur in alluvial sediments (part of the hyporheic zone), shallow base-level streams, flooded caves, lakes in the water table, upper vadose tributaries, and epikarst aquifers. We detected 11 main threats, mainly related to agriculture, pasture, and hydroelectric plans, but unmanaged tourism and pollution are also significant threats. Two threats affect a high number of species (physical change of the habitat and food restriction). The river basins with the higher number of identified threats are the upper Tocantins (eight) followed by the upper Paraguaçu (six). Effective proposals to protect this neglected component of the Brazilian biodiversity are still scarce, such as monitoring projects and their function in the subterranean communities, besides education projects aiming to develop public awareness.摘要 本研究系统梳理了巴西地下鱼类 (subterranean fishes) 所面临的各类威胁相关信息。目前已知该类群至少有36个物种，其中22种已完成正式分类描述，且绝大多数为特有种。在保护现状方面，这类地下鱼类普遍被列为受威胁物种：已正式描述的物种中，绝大多数被纳入巴西国家受威胁动物名录，而仅有4种被列入国际自然保护联盟 (International Union for Conservation of Nature, IUCN) 全球受威胁物种名录。就栖息生境而言，巴西地下鱼类的分布范围涵盖冲积沉积物 (属于潜流带 (hyporheic zone) 的一部分)、浅基准面溪流、淹没洞穴、地下水位带湖泊、包气带 (vadose zone) 上游支流以及表层岩溶含水层 (epikarst aquifers)。本研究共识别出11类主要威胁，其中以农业、畜牧业以及水电规划相关活动为主，无管制旅游与污染同样构成显著威胁；生境物理改变与食物资源限制这两类威胁对大量物种造成影响。受威胁物种数量最多的河流流域为托坎廷斯河上游 (8种)，其次为帕拉瓜苏河上游 (6种)。目前针对巴西生物多样性中这一被忽视类群的有效保护方案仍较为匮乏，除旨在提升公众保护意识的宣教项目外，针对其在地下群落中功能的监测项目同样稀缺。