More than 600 fish, including six eels and nearly 200 bass, discovered in small pools left in fish passage near Sunbury dam during rescue and study

Middle Susquehanna Riverkeeper John Zaktansky relays a net full of fish from Susquehanna University's Dan Ressler to a nearby bucket during an electrofishing pool study and rescue project near Sunbury.

More than 600 fish were rescued from several small pools left in the fish passageway around the Adam T. Bower Memorial Dam on Nov. 27, 2024, by members of the Middle Susquehanna Riverkeeper Association in partnership with Sara Ashcraft and Dan Ressler of Susquehanna University.

“When they built the new passageway around the Fabridam, there were four pools added for fish to have resting spots in what typically is a faster moving channel,” said Middle Susquehanna Riverkeeper John Zaktansky. “However, when the bags are deflated in the offseason, the water no longer flows through the channel, and it left some pools disconnected from the river the fish stranded.”
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Instead of just attempting to catch and release them back into the river, Zaktansky felt it was a good opportunity to partner with Susquehanna University for research and education.

​“To my knowledge, there is limited info on what types of fish species make it to, and through, this dam structure,” he said. “This felt like the perfect opportunity to start seeing what may be here and, by assessing what was left in the pools, having a better idea of what may be using the passageway.”

Sara Ashcraft, Freshwater Research Institute Ecologist with Susquehanna University, and Dr. Dan Ressler, Associate Professor of Earth & Environmental Sciences at the university, used electrofishing backpacks to help improve collection rate of fish at each pool.

Species were then identified and counted, some were weighed and measured, and then they were all released back into the nearby Susquehanna River.

“Getting this information will be an interesting baseline. We now have a better idea of how to proceed in the future in terms of data to collect, timeframe, manhours, equipment needed, that kind of thing,” said Ashcraft. “From here, we can develop questions that will hopefully help DCNR with management of the fish passage and ability to answer public inquiries.

“Studying the connectivity of the fish passage during high water events or Fabridam inflation/deflation could help us understand how these fish are migrating along the mainstem, at least on the Shamokin Dam side of the river.”

In Pool 1, which is the farthest from the river and closest to the Shamokin Dam parking lot, yielded a total of 176 fish, with a large majority of those (132) Smallmouth Bass (75 percent). The next highest populations in this pool, which measured 23 feet wide and 56.5 feet long, were of Mimic Shiners and Greenside Darters at 11 each. One of the most interesting finds included four juvenile American Eels which measured between 200 and 250 mm (7.8 to 9.8 inches) in length.

Other species represented in Pool 1 included Rock Bass (3), Fantail Darters (3), White Suckers (2), Bluntnose Minnows (2) and one each of a Central Stoneroller, Pumpkinseed, Yellow Bullhead, Northern Hogsucker, Black Crappie, Banded Darter, Margined Madtom and Largemouth Bass.

“The concentration of fish in that first pool, especially the high rate of Smallmouth Bass to other species, was really interesting, especially considering it had been well more than a month since the bags had been deflated and that pool has been cut off from the river,” said Zaktansky. “What made it stick out even more was the huge contrast in species found in the second pool in comparison to the first.”

Pool 2 was more narrow, with a deeper channel in the middle and several large rocks that provided good structure/habitat. It measured 18 feet wide by 42 feet long. This pool’s yield was noticeably different than the first, with a total of 447 fish captured and returned to the river.

Of that, an overwhelming majority were tiny feeder fish – minnows, darters, etc. This included 132 Shallowtail Shiners and 36 Mimic Shiners. In stark comparison to the first pool, only 13 Smallmouth Bass were identified.

The biggest surprise, however, came in the form of two adult American Eels which measured approximately 700 mm (27 inches) and 620 mm (24 inches) respectively. An additional juvenile eel was also caught and comparable to the ones caught in the first pool (226 mm/8.9 inches).

Other species identified in the second pool included Rock Bass, Rosyface Shiner and Bluntnose Minnow.

Due to time constraints, individual species identification needed to be ceased part-way through the data collection near the end of work at Pool 2, and a final tally of additional general fish regardless of species was 259.

A quick pass was done in the third pool in the passageway with minimal results. It was still connected partially to the river, allowing fish access back to the Susquehanna. Twenty Smallmouth Bass, two Rock Bass and one Largemouth Bass were collected and transported to the river before wrapping up for the day.

“We definitely found a lot of Smallmouth Bass at every size range. We also saw what could be mature American Eels migrating down the river to spawn, along with yellow eels hanging out in the mainstem or trying to make their way further upstream,” reflected Ashcraft. “Another thing that was interesting was the number of smaller-bodied fishes like minnows, darters and a madtom and bullhead, the latter of which are benthic, meaning they like to be on the bottom of the riverbed.

“We did not see any American Shad, which is probably due to the timing of sampling. These fish are usually moving upstream in the Susquehanna River April through June.”

Pennsylvania Fish and Boat Waterway Conservation Officer Jacob Angstadt-Bennett stopped in to check in on the operation and was glad to see that everything worked out the way that it did.

“I did not expect the catch rate to be that high. I was excited to see an adult eel, as well as several juveniles, utilizing the passage. This shows that current stocking and fish passage efforts are having an impact,” he said. “Additionally, seeing numerous species inside the pools suggests that fish are likely using the passage while it is operational.”

Because the passageway fills during high-water events in different seasons, and runs whenever the Fabridam bags are inflated, the need to address fish stranded in the pools will become a regular project, admitted DCNR Park Manager Trainee Nathan Knox.

“This will be a recurring thing every year when the dam is deflated and anytime there is a high-water event, so we look forward to future work,” he said. “It also offers a great educational opportunity.”

The key, added Zaktansky, will be timing.
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“It will be interesting in the future to see what species are in the pools closer to the loss of water in the passageway before herons and cormorants and other predators start picking off various fish. That may provide a better idea of what is moving through there, at least during that season of the year,” he said. “And also to compare fish diversity in each pool earlier in the process before they start feeding on each other over a lengthy period of time.”

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