A North American river otter has been photographed in the Bronx section of the Bronx River for the first time in about 100 years.Local scientist RJ Hawkins captured the image with a motion-activated camera while monitoring wildlife with oversight from the Wildlife Conservation Society's Education Department at the Bronx Zoo.River otters need clean water, healthy habitat, and enough fish to live. Their appearance is a sign that the river is becoming more welcoming to native wildlife.The sighting follows decades of work by public agencies, nonprofit groups, conservation partners, and community volunteers to improve the Bronx River. Researchers caution that one photograph does not prove a resident population, but it is an encouraging sign of recovery.