Data supporting Conservation relevant fine-scale distribution and habitat associations of threatened elasmobranchs in temperate nearshore waters

Elasmobranchs are globally threatened and experiencing ongoing declines. Understanding threatened elasmobranch distribution is critical for developing effective marine conservation strategies. However, our knowledge of fine scale elasmobranch habitat association and distribution in temperate nearshore systems is limited. Here, we examined the presence, relative abundance and habitat association of sharks, skates and rays using benthic baited remote underwater stereo-video systems (SBRUVs). From 772 deployments (682 total hours, 53 minutes average soak time) across three years (2021-2023) and two Scottish sea lochs and adjacent bays, elasmobranchs were detected on 31.2% of deployments (n = 241). Our surveys detected six species of elasmobranchs, flapper skate (<i>Dipturus intermedius</i>), thornback ray (<i>Raja clavata</i>), spotted ray (<i>Raja montagui</i>), lesser spotted dogfish (<i>Scyliorhinus canicula</i>), spiny dogfish (<i>Squalus acanthias</i>) and porbeagle (<i>Lamna nasus</i>) representing 17.6% of the resident elasmobranch diversity reported to date in UK nearshore waters &lt; 200 m depth. The species detected include two species listed as globally Vulnerable on the IUCN Red List, spiny dogfish and porbeagle and one Critically Endangered species, flapper skate. Critically Endangered flapper skate were detected in 5.2% deployments (n = 40) and were the only species recorded which did not show a relationship between the probability of presence and substratum type. Our findings provide critical data on the fine scale spatial distribution and substrate associations of elasmobranchs, which could be used to inform evidence-based conservation measures and support more consistent and targeted policy action for these species in Scotland.

板鳃类（Elasmobranchs）在全球范围内面临生存威胁，种群数量持续衰退。明确受威胁板鳃类的分布格局，对于制定高效的海洋保护策略至关重要。然而，目前学界对温带近岸系统中板鳃类的精细尺度生境关联与分布模式的认知仍较为匮乏。本研究采用底栖诱捕式水下立体视频系统（SBRUVs），对鲨类、鳐类与魟类的存在情况、相对丰度及生境关联展开调查。研究于2021-2023年三年间，在两处苏格兰海峡湾及邻近海湾开展了772次布放作业，总时长682小时，平均布放时长为53分钟。其中31.2%的布放作业（n=241）中检测到板鳃类。本次调查共记录6种板鳃类：扇鳐（flapper skate，<i>Dipturus intermedius</i>）、棘鳐（thornback ray，<i>Raja clavata</i>）、斑鳐（spotted ray，<i>Raja montagui</i>）、小斑猫鲨（lesser spotted dogfish，<i>Scyliorhinus canicula</i>）、白斑角鲨（spiny dogfish，<i>Squalus acanthias</i>）与鼠鲨（porbeagle，<i>Lamna nasus</i>），上述物种占英国近岸水深200米以浅海域迄今已报道的常驻板鳃类物种多样性的17.6%。本次记录的物种中，有2种被IUCN红色名录列为全球易危物种：白斑角鲨与鼠鲨；另有1种被列为极危物种：扇鳐。极危物种扇鳐在5.2%的布放作业中被检测到（n=40），是唯一未表现出存在概率与底质类型存在关联的物种。本研究结果为板鳃类的精细尺度空间分布与底质关联提供了关键实证数据，可用于指导循证保护措施的制定，助力苏格兰地区针对此类物种出台更具一致性与针对性的政策行动。