St. Mary's Lake in St. Mary's County and Deep Creek Lake in Garrett County have Christmas trees at their bottoms, Mr. Cosden said.
"There's a lot of benefits to having the trees," said Don Cosden, manager of the inland fisheries division of the Maryland Department of Natural Resources. "Tree limbs or other kinds of structure with little spaces provide things for your basic food-chain organisms, like algae, to get started. Then other critters come along. It's a benefit to the basics of the food chain. It's a benefit to young fish who use it to hide from predators, and even larger fish tend to hide close to the structure and use it as a cover or an ambush point."