Fish community survey data from 23 inland lakes of Isle Royale National Park (1929–2024)

Fish communities are shaped by environmental filters operating across different spatiotemporal scales. While many recent studies focus on anthropogenic gradients, few can isolate the role of natural drivers in community assembly. Isle Royale’s inland lakes offer a rare opportunity to explore long-term fish biodiversity dynamics with minimal confounding influences. We analyzed fish communities in 23 lakes surveyed in the 1920s, 1990s, and 2020s to 1) assess temporal changes in richness and composition 2) identify lakes and species experiencing the greatest change, and 3) evaluate environmental drivers of community structure. We analyzed historical and contemporary fish survey data using species-area curves, PERMANOVA, and multivariate dispersion tests to quantify changes in richness and composition, temporal beta biodiversity indices and similarity percentage (SIMPER) to identify lakes and species changing most, and non-metric multidimensional scaling (NMDS) to examine relationships with..., , # Isle Royale fish biodiversity trends

Dataset DOI: [10.5061/dryad.h44j0zpzv](10.5061/dryad.h44j0zpzv)

## Description of the data and file structure

These files contain the data and code for analyses in Gallagher et al. (in preparation), who address 1) how fish species richness and composition have changed in the inland lakes of Isle Royale National Park between the 1920s, 1990s, and 2020s, 2) which fish species and lakes have changed most, and 3) which environmental drivers most strongly influence current community structure. Historical data from the 1920s (Koelz 1929) and 1990s (Kallemeyn 2000) were combined with recent data from a 2020s survey for analyses. Conventional survey methods included gillnets, minnow traps, beach seines, angling, and stomach content analysis. Species richness data include the total number of species found in each lake during each survey, as well as lake surface areas. Species composition data include presence-absence data for each lake during each surv...,