KYAW MOE, A FIELD BIOLOGIST from Myanmar, learns how to handle a fyke net. He’s pulling diamondback terrapins out of a creek off the Patuxent River that’s now lined with large homes and new lawns where terrapins used to nest. He’s here for training with Willem Roosenburg (below, center), a biologist who’s been running a long-term research project on his hometown river. Helping with his mark-and-recapture study are Margaret Lilly and Tom Parker, students from the University of Maryland where the terrapin reigns as the school mascot. Each diamondback is notched with a long-lasting ID, then weighed and measured, sexed and aged — and finally released back into the river. Over 22 years Roosenburg has more than 30,000 captures of more than 10,000 terrapins. Photographs by Michael W. Fincham.