Yonathan Zohar, Jorge Gomezjurado and Odi Zmora check on bluefin tuna larvae in tanks at the University of Maryland Baltimore County's Institute of Marine and Environmental Technology. Courtesy of Yonathan Zohar hide caption

itoggle caption Courtesy of Yonathan Zohar

Guided by biologists, volunteers briefly catch, band and release some of Delaware's visiting red knots each spring to monitor the health of the species. Maggie Starbard/NPR hide caption

itoggle caption Maggie Starbard/NPR

Using dipnets --€” which have nets up to 5 feet in diameter at the end --€” isn't easy, and the river can get pretty crowded. Robert Carter, a novice dipnetter, holds up the first fish he caught after a day on the Kenai River. Annie Feidt/Alaska Public Media hide caption

itoggle caption Annie Feidt/Alaska Public Media

Arturo, the only polar bear in Argentina, lives in captivity at a zoo in Mendoza. The plight of the "sad bear" has spawned more than 400,000 signatures on a petition to get him moved to a "better life" in Canada. AFP/Getty Images hide caption

itoggle caption AFP/Getty Images

Members of the Bird Ambassadors program painted and planted a broken canoe at a Baltimore charter school in November. The canoe was filled with species native to Maryland, providing food and habitat for local birds. Susie Creamer/Courtesy of Patterson Park Audubon Center hide caption

itoggle caption Susie Creamer/Courtesy of Patterson Park Audubon Center