Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
Institute of Marine Sciences, University of Dar Es Salaam, Zanzibar, Tanzania.
Sci Rep. 2022 Mar 9;12(1):4196. doi: 10.1038/s41598-022-07931-9.
Fish larvae supply in nearshore vegetated habitats, such as seagrass meadows and mangroves, contributes significantly to sustainable fish stocks. Yet, little information is available on distribution patterns of fish larvae in mangrove and seagrass habitats of the western Indian Ocean. The present study investigated the abundance, diversity and assemblage composition of fish larvae in mangrove creeks, inshore seagrass meadows (located adjacent to mangroves) and nearshore seagrass meadows (located in-between mangroves and coral reefs) in two coastal seascapes of Zanzibar (Tanzania) across seasons for 1 year. The highest mean abundances of fish larvae were recorded in mangrove creeks, while nearshore- and inshore seagrass meadows showed similar mean abundance levels. Generally, fish larvae representing 42 families were identified, with the fourteen most abundant families comprising 83% of all specimens. Fish larvae communities were dominated by specimens of the postflexion growth stage in all habitats, except in mangrove creeks in one of the two seascapes (i.e. Chwaka Bay) from April through June when abundances of the preflexion and very small-sized individuals were exceptionally high. Slightly higher fish larvae abundances were observed in mangroves during the southeast monsoon compared to the northeast monsoon, and there were also differences across months within monsoon periods for all three habitats studied. Assemblage composition of larvae did, however, not vary significantly in time or space. Our findings suggest that mangroves and seagrass meadows are highly linked shallow-water habitats with high retention of fish larvae contributing to similarity in assemblage compositions across shallow coastal seascapes. Conservation and management efforts should prioritize connected shallow-water seascapes for protection of fish larvae and to uphold sustainable coastal fisheries.
近海植被栖息地（如海草草甸和红树林）中的鱼类幼体供应对可持续鱼类种群有重要贡献。然而，关于印度洋西部红树林和海草草甸栖息地中鱼类幼体的分布模式的信息很少。本研究调查了坦桑尼亚桑给巴尔两个沿海海域的红树林溪、近岸海草草甸（位于红树林附近）和近海海草草甸（位于红树林和珊瑚礁之间）在 1 年的季节中的鱼类幼体的丰度、多样性和组合组成。在所有栖息地中，鱼类幼体代表 42 个科，其中最丰富的 14 个科占所有标本的 83%。除了在两个海域之一的查瓦卡湾（Chwaka Bay）的 4 月至 6 月期间，前屈和非常小体型个体的丰度异常高之外，所有栖息地中的鱼类幼体群落均以后屈生长阶段的标本为主。在东南季风期间，红树林中的鱼类幼体丰度略高于东北季风，在季风期间的所有三个栖息地中，每月之间也存在差异。然而，幼虫的组合组成在时间或空间上没有显著变化。我们的研究结果表明，红树林和海草草甸是高度相关的浅水栖息地，鱼类幼体的高保留率导致浅水沿海海域的组合组成相似。保护和管理工作应优先考虑连接的浅水海域，以保护鱼类幼体并维持可持续的沿海渔业。
