Using Aerial Imagery and Fish Capture Data to Estimate Juvenile Pacific Salmon Abundance

Cataloging and monitoring of freshwater rearing habitat is critical for developing ecosystem-based management goals for Pacific Salmon in Alaska.  However, in remote areas of the state this process becomes logistically and financially difficult. Remote sensing methods have been used in recent decades to address these challenges with varying success. This project explored the use of aerial digital imagery and fish capture data for long-term monitoring of freshwater salmon rearing habitat in the Togiak National Wildlife Refuge (TNWR), Alaska.  In 2010, TNWR acquired airborne digital photographs in the visible light, near infrared and thermal range of instream habitat in two small study areas in the Kulukak River basin.  In addition, multiple-removal electrofishing was used to estimate juvenile salmon abundance in a sample of the habitat types detected through the aerial photography.  Combining estimates of juvenile abundance by habitat type and area of habitat by type derived from the classified imagery yielded juvenile salmon density by species and habitat type for the two study areas.  In this presentation, I will elaborate on the quality of the density estimates obtained, and discuss possible causes and suggestions for incorporating these methods into future freshwater salmon habitat monitoring plans in southwest Alaska.