Faculty of Advanced Science and Technology, Kumamoto University, Kurokami, Chuo-ku, Kumamoto, Japan.
Department of Civil and Environmental Engineering, Kumamoto University, Kurokami, Chuo-ku, Kumamoto, Japan.
PLoS One. 2020 Dec 23;15(12):e0244494. doi: 10.1371/journal.pone.0244494. eCollection 2020.
The tri-spine horseshoe crab, Tachypleus tridentatus, is a threatened species that inhabits coastal areas from South to East Asia. A Conservation management system is urgently required for managing its nursery habitats, i.e., intertidal flats, especially in Japan. Habitat suitability maps are useful in drafting conservation plans; however, they have rarely been prepared for juvenile T. tridentatus. In this study, we examined the possibility of constructing robust habitat suitability models (HSMs) for juveniles based on topographical data acquired using unmanned aerial vehicles and the Structure from Motion (UAV-SfM) technique. The distribution data of the juveniles in the Tsuyazaki and Imazu intertidal flats from 2017 to 2019 were determined. The data were divided into a training dataset for HSM construction and three test datasets for model evaluation. High accuracy digital surface models were built for each region using the UAV-SfM technique. Normalized elevation was assessed by converting the topographical models that consider the tidal range in each region, and the slope was calculated based on these models. Using the training data, HSMs of the juveniles were constructed with normalized elevation and slope as the predictor variables. The HSMs were evaluated using the test data. The results showed that HSMs exhibited acceptable discrimination performance for each region. Habitat suitability maps were built for the juveniles in each region, and the suitable areas were estimated to be approximately 6.1 ha of the total 19.5 ha in Tuyazaki, and 3.7 ha of the total 7.9 ha area in Imazu. In conclusion, our findings support the usefulness of the UAV-SfM technique in constructing HSMs for juvenile T. tridentatus. The monitoring of suitable habitat areas for the juveniles using the UAV-SfM technique is expected to reduce survey costs, as it can be conducted with fewer investigators over vast intertidal zones within a short period of time.
三刺东方鲎，Tachypleus tridentatus，是一种受威胁的物种，栖息在从南亚到东亚的沿海地区。迫切需要建立一个保育管理系统来管理其育幼栖息地，即潮间带，特别是在日本。生境适宜性图在起草保护计划时很有用；然而，它们很少为幼年三刺东方鲎编制。在这项研究中，我们检查了使用无人机和运动结构（UAV-SfM）技术获取的地形数据为幼鲎构建稳健生境适宜性模型（HSM）的可能性。2017 年至 2019 年，在津崎和今津潮间带确定了幼鲎的分布数据。这些数据被分为用于 HSM 构建的训练数据集和用于模型评估的三个测试数据集。使用 UAV-SfM 技术为每个区域建立高精度数字表面模型。通过转换考虑每个区域潮差的地形模型来评估归一化高程，然后根据这些模型计算坡度。使用训练数据，以归一化高程和坡度作为预测变量构建了幼鲎的 HSM。使用测试数据评估 HSM。结果表明，HSM 对每个区域都表现出可接受的区分性能。为每个区域的幼鲎构建了生境适宜性图，并估计适宜区域在津崎约为 19.5 公顷的 6.1 公顷，在今津约为 7.9 公顷的 3.7 公顷。总之，我们的研究结果支持使用无人机 SfM 技术为幼年三刺东方鲎构建 HSM 的有效性。使用 UAV-SfM 技术监测幼鲎的适宜栖息地区域有望降低调查成本，因为它可以在短时间内由较少的调查人员在广阔的潮间带进行。
