As the state of non-marine aquatic environments (freshwater and estuarine environments with salinities ≤ 30 ppt) continues to decline globally, there is increasing concern for elasmobranchs (sharks and rays) that use them at critical stages of their life history. Due to a range of impediments including unresolved taxonomy, lack of fisheries data, and poor public perception, our knowledge of elasmobranchs in non-marine environments has lagged behind marine species. Here, we refine previous categorisations of elasmobranchs that occur in non-marine environments by reviewing the timing and duration of freshwater (≤ 5ppt) and/or estuarine (> 5 to ≤ 30 ppt) habitat use throughout each species’ life history. We identified five categories describing elasmobranchs in non-marine environments: (1) freshwater obligates (43 spp.); (2) euryhaline generalists (10 spp.); (3) estuarine generalists (19 spp.); (4) non-marine transients; (5) non-marine vagrants. Criteria for species inclusion is provided for all categories, and species lists are presented for categories 1–3. Euryhaline and estuarine generalists had the highest number of species that are threatened with extinction on the IUCN Red List of Threatened Species (50% and 65%, respectively), and freshwater obligate species have a very high portion of Data Deficient and Not Evaluated species (77%). The refinement of non-marine elasmobranch categories will aid in our understanding of elasmobranchs that occur in non-marine environments, helping facilitate more strategic conservation and management initiatives. Research on the biology of elasmobranchs and their human interactions in non-marine environments are suggested, as this will lead to better availability of information for conservation and management.

中文翻译：

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弹性鳃类对非海洋环境的使用模式进行分类并审查它们的灭绝风险

随着非海洋水生环境（盐度≤ 30 ppt 的淡水和河口环境）在全球范围内持续下降，人们越来越关注在其生命史的关键阶段使用它们的弹鳃类动物（鲨鱼和鳐鱼）。由于一系列障碍，包括未解决的分类学、缺乏渔业数据和公众认知度差，我们对非海洋环境中的弹鳃类动物的了解落后于海洋物种。在这里，我们通过审查淡水 (≤ 5ppt) 和/或河口 (> 5 至 ≤ 30 ppt) 栖息地使用的时间和持续时间，完善了之前对非海洋环境中出现的弹性鳃类动物的分类。我们确定了描述非海洋环境中的 elasmobranch 的五个类别：（1）淡水专性（43 种）；(2) 广盐通才 (10 spp.); (3) 河口通才（19 人）；(4) 非海洋瞬变；(5) 非海洋流浪者。为所有类别提供了物种包含标准，并为类别 1-3 提供了物种列表。在 IUCN 濒危物种红色名录中，广盐性和河口通才的物种数量最多（分别为 50% 和 65%），淡水专性物种的数据不足和未评估物种的比例非常高（ 77%）。对非海洋硬鳃类动物类别的细化将有助于我们了解发生在非海洋环境中的软鳃类动物，有助于促进更具战略性的保护和管理举措。建议在非海洋环境中研究 elasmobranchs 的生物学及其与人类的相互作用，