Relating spatial distributions of acoustically determined patches of fish and plankton: data viewing, image analysis, and spatial proximity

We developed a point-and-click acoustic data viewer (FishViewer) for explor atory comparison of up to three acoustic survey transects (or three frequen cies) at a time and other environmental and biological data (e.g., surface temperature and seabird abundance). FishViewer also contains image-processi ng tools (e.g., morphological and threshold filters) for distinguishing bet ween fish shoals and plankton patches and for patch identification. These t ools and methods are illustrated using survey data collected at three frequ encies (38, 120, and 200 kHz) near the Pribilof Islands, Bering Sea, during September 1995. Data were also visualized by converting the patches identi fied in the acoustic images to polygons, showing the boundaries of each pat ch using a connected component algorithm. Proximity between these fish shoa l and plankton patch polygons was examined statistically using an interval- based nonparametric regression model (generalized additive models) and a di stance-based proximity measure. The methods presented for data refinement, visualization, and the establishment of fish-plankton patch proximity serve as a paradigm for scale-robust hypothesis formulation and testing of spati al patterns of fish and plankton.