Seascape complexity and habitat heterogeneity influence Alaskan eelgrass fish assemblages

Enclosed data and code are an archive for submitted manuscript "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.