Claire Corlett

Fish Food, Fish Tanks, and More
Rock Creek Fish Ladder

Rock Creek Fish Ladder

Out in the Atlantic Ocean, fish like the river herring make their home in the open waters. They compete with other species, dodge predators, and swim free in the saltwater. Though the ocean is a prime habitat for fish growth, it may not be the best place for a little herring to hatch. Anadromous fish like river herring are a special type of fish that live in the ocean but lay their eggs in fresh water. So those herring that reach maturity head back to a freshwater river to lay their eggs. In the spring, they swim up the Chesapeake Bay and into the freshwater rivers like those where they were born, each striving to contribute to the next generation of
herring. Some swim north through the Potomac River and eventually find their way up to Rock Creek Park. But here, they hit a wall. In 1903, a decorative waterfall was built on Rock Creek, four miles from the Potomac River
at Peirce Mill, creating a beautiful water feature for the historic mill, but a big problem for the migrating fish! Obstacles like this one once blocked the fish passage, making it impossible for fish to get to the safe waters upstream to lay their eggs. Luckily everything changed when in 2006 Rock Creek Park reopened 21 miles of the
creek to the fish whose ancestors were born here. But the waterfall at Peirce Mill still blocks the creek — so how are fish getting around it? They climb a ladder, of course! “A fish ladder is a structure that is built and designed to permit the movement of fish above a barrier of some kind, and it could be a sewer line, or in the case of Rock Creek, it’s a historic dam that’s 8 feet tall. There’s a baffle that will increase in height as you go from the bottom of the
fish ladder to the top. The fish ladder is built so that fish can move past the dam, up the series of baffles, to continue upstream.” Now that the fish can come home to lay their eggs, a new generation of river herring
and shad are able to hatch in the safety of Rock Creek before they swim back downstream to the ocean. Maybe one day, if they’re lucky, they’ll find their way back to Rock Creek again.

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