Philadelphia’s Fish Ladder on the Schuylkill River

The Schuylkill River flows through 123 miles of eastern Pennsylvania, making it one of the Keystone State’s largest and most important waterways. Its entire watershed is 2,000 square miles and stretches across eleven counties, flowing from the Schuylkill Highlands through the Lehigh Valley, and then into Southeastern Pennsylvania where it joins the Delaware River in south Philadelphia.

A river once rich in fish

Historically home to a wide diversity of fish species, the Schuylkill River once supported large populations of the American shad. Sometimes called “the fish that fed the nation’s founders,”[1] this large herring was once abundant in rivers like the Schuylkill. The shad live predominantly in the Atlantic Ocean but travel up freshwater rivers to spawn. Once a common fish throughout the Atlantic coastal region, the damming of rivers like the Schuylkill, Susquehanna, and Hudson had cut off the shad from their inland breeding grounds, nearly wiping them out along the U.S. Eastern seaboard[2].

The American shad.Photo by Sherman Foote Denton via Wikimedia | Public Domain

The Fairmount Dam, located on the Center City Philadelphia stretch of the Schuylkill River, has been one such barrier. Constructed in 1818 to help divert water into the newly constructed pump house at the Fairmount Water Works in order to supply water to the growing city, the Fairmount Dam effectively prevented all migratory species of fish from swimming upstream along the Schuylkill River from 1818 until 1979[3].

In 1977, construction began on the first fish ladder (also called a “fishway”) on the lower Schuylkill River, on the western side of the Fairmount Dam. The goal of this project was to reestablish the shad historic migration route – known as a “shad run” – and reopen the Schuylkill River to other migratory fish species. Shortly following completion of the ladder in 1979, the Pennsylvania Fish and Boat Commission (PFBC) observed 33 species using this new fishway, including key migratory species of interest like the river herring, American shad, and striped bass. By 1984, striped bass were seen spawning several miles upstream of the Fairmount Dam at the Flat Rock Dam in Manayunk – likely the first population to do so in the Schuylkill River in over 150 years – which indicated they were successfully using the fishway. However, surveys by the PFBC consistently found significantly higher populations of American shad, alewives, blueback herring, and white perch below the dam than above the dam, indicating use of the ladder by migrating fish was still limited[4].

The Fairmount Dam seen from the west in 1980.Photo by Jack Boucher, Library of Congress | Public Domain

There were two problems: First, the structure itself quickly accumulated debris that blocked fish passage, requiring continuous maintenance.

A second problem was that, after 161 years, no shad “knew” to use the Schuylkill River to spawn. Shad, like many other migratory fish, imprint on their own spawning ground as juvenile fish, known as fry, and return to the same place as an adult.

After the initial construction of the fish ladder, it appeared that the only shad using it were those that got lost in their attempt to navigate up the undammed Delaware River. So to effectively reestablish the Schuylkill shad run, two further steps were needed: 1) for the ladder to be redesigned, and 2) for young shad to be “shown” the way[5].

To address these challenges the existing fish ladder had to be rebuilt and improved. This was completed in 2008, with the new structure’s entrance, exits, and pools designed to mimic the natural experience of swimming upstream. The changes were a success: when paired with upstream introductions of shad fry by the PFBC, shad populations in the Schuylkill River jumped dramatically. By 2011, over 3,000 American shad were ascending the ladder, versus the dozens seen a year before the upgrades. Other migratory fish like blueback herring and striped bass increased as well[6].

For a fish swimming up the Schuylkill River, addressing the migratory hurdle created by the Fairmount Dam was only the first impediment. Since then, new fishways and recent dam removals have made it so that migratory fish can now travel 100 miles upriver on the Schuylkill unimpeded[7].

Otters getting a leg up

And fish are not the only beneficiaries. In recent years, river otters have begun using the fish ladder to navigate upstream. By the end of the 1800s, industrial pollution and unregulated trapping had nearly driven the region’s river otters to extinction. Limits on trapping, combined with work to clean up the region’s waterways, have brought the Delaware River’s otter populations back from the brink, and their numbers continue to increase throughout the watershed[8]. As the otter population rebounds in the Delaware River and the water quality of the Schuylkill River improves, otters in need of additional habitat are using fishways like the Fairmount Fish Ladder to repopulate their historic range[9].

An otter is uses the Fairmount Fish Ladder.Photo by Philadelphia Wateer Department | Used by permission

References

1. Timothy B. Wheeler, “Once nearly wiped out, shad stage an uneven comeback in the Chesapeake Bay,” Baltimore Sun, 8 May 8, 2019.

2. Ibid.

3. U.S. Army Corps of Engineers, Philadelphia District. Finding of no significant impact: Fairmount Dam Fish Ladder Project, January 2004.

4. Ibid.

5. Ibid.

6. Stephen Rochette, United States Army. Philadelphia fish passage proving successful (blog post), 27 April 27.

7. Ibid.

8. Brodhead Watershed Association, “Nature at risk: Otters still call Delaware River home, for now”, Pocono Record, 11 August 2022.

9. Brian Hickey, “Yes, more otters are calling the
Schuylkill River in Philadelphia home,” Philly Voice, 22 June 2016.