New perspectives in the analysis of fish distributions: A case study on the spatial distribution of largemouth bass

Analyses of fish distributions rarely account for spatial arrangement of habitat types, are typically conducted at a single scale, and use a null model of random distributions without considering other null models. This study demonstrates a procedure to circumvent these difficulties by analyzing telemetry data collected on largemouth bass (Micropterus salmoides) in Long Lake, Michigan. Bass were highly aggregated within the littoral region, showing peaks of aggregation at small (<60 m) and large (>160 m) spatial scales. A neutral movement model (no taxis or kinesis within habitat types) could explain some of the observed aggregation, yet substantial aggregation remains unexplained. Much of the large-scale aggregation could be generated by including a taxis towards the eastern half of the basin, but taxes towards shallower cells or cells containing woody emergent macrophytes were unable to generate the observed degree of small-scale aggregation. Our results highlight the utility of analyzing spatial distributions at multiple scales and the importance of the spatial arrangements of habitat types and suggest that nonrandom distributions at one scale may be due to processes occurring at different scales.