Monitoring the expanding distribution of nonindigenous dwarf eelgrass Zostera japonica in a Pacific Northwest USA estuary using high resolution digital aerial orthophotography

The paper describes a method of mapping the intertidal distribution of the nonindigenous seagrass Zostera japonica in a Pacific Northwest (PNW) USA estuary from color infrared aerial orthophotography using a hybrid digital classification technique. A random ground survey indicated an overall accuracy exceeding 80 percent for this procedure in the lower estuary, where this invasive species may interfere with mudflat foraging of the commercially important Dungeness crab. Knowledge of the areal distribution of Z. japonica from this digital classification will aid in planning studies to evaluate impacts of expansion of the nonindigenous seagrass in PNW estuaries.