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Confluences function as ecological hotspots: geomorphic and regional drivers can help identify patterns of fish distribution within a seascape

Ryland Taylor*, Martha Mather, Joseph Smith, Kayla Gerber

*Corresponding author:

ABSTRACT: Quantifying heterogeneity in animal distributions through space and time is a precursor to addressing many important research and management issues. Obtaining these distributional data are especially difficult for mobile organisms that use broader geographic extents. Here we asked if the merger between two research directions − (1) quantifying spatial linkages between fish and geomorphic features (e.g., confluences) and (2) analyzing larger-scale, multi-metric organismal patterns − can provide a broader geographic context for ecological issues that depend on understanding dynamic fish distribution. To address these objectives, we collected data from 59 tagged striped bass (Morone saxatilis) that were detected by a 26-acoustic receiver array deployed within Plum Island Estuary, MA, USA. We examined these telemetry data using generalized linear mixed models and chi-square, cluster, network analyses. Geomorphic site types informed the estuary-wide distribution of striped bass in that tagged fish spent the most time at confluence junctions. However, fish did not spend the same amount of time at all estuarine confluence junctions. Relative to integrating multiple metrics, number of tagged fish, residence time, and number of movements were not the same across all receivers. When all three metrics were considered together, four distinct clusters of distributional patterns emerged. Network analyses connected geomorphology and multi-metric seascape patterns. Confluence junctions in the Rowley and Middle regions were the most connected (high centrality) and most used sites (high residence time). Although confluence junctions function as ecological hotspots, researchers and managers will benefit from interpreting geomorphology within a larger geographic context.