Ecosystems are linked by the movement of organisms across habitat boundaries and the arrangement of habitat patches can affect species abundance and composition. In tropical seascapes many coral reef fishes settle in adjacent habitats and undergo ontogenetic habitat shifts to coral reefs as they grow. Few studies have attempted to measure at what distances from nursery habitats these fish migrations (connectivity) cease to exist and how the abundance, biomass and proportion of nursery species change on coral reefs along distance gradients away from nursery areas. The present study examines seascape spatial arrangement, including distances between habitats, and its consequences on connectivity within a tropical seascape in Mozambique using a seascape ecology approach. Fish and habitat surveys were undertaken in 2016/2017 and a thematic habitat map was created in ArcGIS, where cover and distances between habitat patches were calculated. Distance to mangroves and seagrasses were significant predictors for abundance and biomass of most nursery species. The proportions of nursery species were highest in the south of the archipelago, where mangroves were present and decreased with distance to nurseries (mangroves and seagrasses). Some nursery species were absent on reef sites farthest from nursery habitats, at 80 km from mangroves and at 12 km from seagrass habitats. The proportion of nursery/non-nursery snapper and parrotfish species, as well as abundance and biomass of seagrass nursery species abruptly declined at 8 km from seagrass habitats, indicating a threshold distance at which migrations may cease. Additionally, reefs isolated by large stretches of sand and deep water had very low abundances of several nursery species despite being within moderate distances from nursery habitats. This highlights the importance of considering the matrix (sand and deep water) as barriers for fish migration.

中文翻译：

---

海景连通性阈值：苗圃栖息地的空间排列构成了附近珊瑚礁上的鱼类群落

生态系统通过生物跨越栖息地边界的运动而联系在一起，栖息地斑块的排列会影响物种的丰度和组成。在热带海景中，许多珊瑚礁鱼类定居在邻近的栖息地，并随着它们的生长经历个体发育栖息地向珊瑚礁的转变。很少有研究试图测量这些鱼类迁徙（连通性）在距苗圃栖息地的距离有多远，以及珊瑚礁上苗圃物种的丰度、生物量和比例如何沿着远离苗圃区的距离梯度变化。本研究使用海景生态学方法研究海景空间排列，包括栖息地之间的距离，及其对莫桑比克热带海景内连通性的影响。2016/2017 年进行了鱼类和栖息地调查，并在 ArcGIS 中创建了主题栖息地地图，其中计算了栖息地斑块之间的覆盖和距离。到红树林和海草的距离是大多数苗圃物种丰度和生物量的重要预测因子。苗圃物种的比例在群岛南部最高，那里有红树林，并且随着距苗圃（红树林和海草）的距离而减少。一些苗圃物种在距苗圃栖息地最远、距红树林 80 公里和距海草栖息地 12 公里的珊瑚礁地点不存在。苗圃/非苗圃鲷鱼和鹦嘴鱼物种的比例，以及海草苗圃物种的丰度和生物量在距海草栖息地 8 公里处突然下降，表明迁移可能停止的阈值距离。此外，被大片沙子和深水隔离的珊瑚礁尽管距离苗圃栖息地的距离适中，但几种苗圃物种的丰度非常低。这突出了将基质（沙子和深水）视为鱼类洄游障碍的重要性。