Seascape complexity and habitat heterogeneity influence Alaskan eelgrass fish assemblages

Enclosed data and code are an archive for accepted manuscript at MEPS entitled: "Seascape complexity and habitat heterogeneity influence Alaskan eelgrass fish assemblages". We include five scripts, numbered by the order in which they should be run. The first two are scripts that calculate seascape composition and heterogeneity from drone imagery (1) and a cleaning script for all variables involved in analyses (2). The last three are analyses scripts. This includes abundance-based multivariate analysis (3), univariate analysis (pulls data from mv analysis) (4), and biomass-based multivariate analysis (5). These scripts generate all included analyses in manuscript and corresponding figures from analyses. Nearshore marine ecosystems along heterogeneous coasts are composed of dynamic and complex habitats that provide important services including shelter and prey for juvenile, migratory, and residential species. Habitats often intermix, though we regularly study them in isolation without considering surrounding influences. We examined how fish assemblages differ in Southeast Alaska eelgrass meadows when the surrounding seascape includes or does not include adjacent kelp habitat to test the role of spatial arrangement and composition of nearshore coastlines on associated fish assemblages. We characterized habitats using aerial imagery and in-situ sampling while quantifying eelgrass fish assemblages using beach seines. We found increased fish species richness and diversity in eelgrass when kelps are adjacent. The fish assemblage included greater prevalence of lingcod (Ophiodon elongatus), whitespotted greenling (Hexagrammous stelleri), sculpins (Cottoidea), Pacific sand lance (Ammodytes personatus), and pink salmon (Oncorhynchus gorbuscha). Some fish species, however, were more abundant within eelgrass habitat without adjacent habitats, including Pacific staghorn sculpin (Leptocottus armatus), shiner perch (Cymatogaster aggregata), and threespine stickleback (Gasterosteus aculeatus). While both threespine sticklebacks and shiner perch were caught in both types of eelgrass habitats, juveniles of these species were more abundant in eelgrass without other adjacent habitat, highlighting the role of eelgrass as nursery habitat. Seascape complexity, in which nearshore habitats are contextualized, is important for evaluating the role of these habitats for nearshore habitat conservation and fisheries management.随附的数据与代码为一篇已被MEPS接收的手稿的存档文件，手稿标题为：《海景复杂性与生境异质性对阿拉斯加鳗草（eelgrass）鱼类群落的影响》。本存档包含5份脚本，按运行顺序编号排序。前两份脚本分别用于从无人机影像中计算海景组成与异质性（脚本1），以及用于清洗分析中涉及的全部变量的预处理脚本（脚本2）。后三份为分析脚本：分别为基于丰度的多变量分析脚本（脚本3）、单变量分析脚本（从多变量分析中提取数据，脚本4），以及基于生物量的多变量分析脚本（脚本5）。上述脚本可复现手稿中提及的全部分析内容及分析所得的配套图表。 异质海岸带的近岸海洋生态系统由动态复杂的生境组成，这些生境可为幼鱼、洄游性鱼类与定居性鱼类提供庇护场所与食物资源。不同生境往往相互交错，但现有研究常将其单独割裂分析，未考虑周边生境的影响。本研究以阿拉斯加东南部的鳗草草场为研究对象，设置周边海景包含/不包含相邻海带生境两种场景，探究鱼类群落的差异，以此验证近岸海岸线的空间配置与组成对关联鱼类群落的调控作用。研究人员通过航空影像与原位采样对生境进行表征，并利用海滩围网法量化鳗草场内的鱼类群落组成。 研究发现，当周边存在海带生境时，鳗草场内的鱼类物种丰富度与多样性均有所提升。该群落中蛇齿单线鱼（Ophiodon elongatus）、白斑六线鱼（Hexagrammos stelleri）、杜父鱼总科（Cottoidea）、太平洋沙鳗（Ammodytes personatus）以及驼背大马哈鱼（Oncorhynchus gorbuscha）的占比更高。但也有部分鱼类仅在无相邻生境的鳗草生境中丰度更高，包括太平洋鹿角杜父鱼（Leptocottus armatus）、银鲈（Cymatogaster aggregata）以及三刺鱼（Gasterosteus aculeatus）。尽管三刺鱼与银鲈在两种鳗草生境中均有捕获，但这两类物种的幼体在无相邻生境的鳗草场内丰度更高，这进一步凸显了鳗草作为育幼生境的重要作用。 将近岸生境置于海景复杂性的语境下进行考量，对于评估此类生境在近岸生境保护与渔业管理中的作用具有重要意义。