A fishy situation: Sizing up the population in Centennial Lake

Dr. Kathleen Browne encourages students to refrain from fishing in Centennial Lake due to the levels of the decreasing fish population
Dr. Kathleen Browne encourages students to refrain from fishing in Centennial Lake due to the levels of the decreasing fish population

By Emily Klingman

What creatures lurk in the dark, murky waters of Centennial Lake? Last fall, one professor and her science class decided to find out once and for all.

“Lots of people have been observing that the fish numbers had been seeming to drop,” said Dr. Kathleen Browne, professor of geological, environmental and marine sciences. “And since 2000 or so, we’ve been monitoring the lake for a variety of reasons, like water chemistry and the shoreline restoration in 2002.”

It was during one of Browne’s introductory science courses that she came up with the idea of conducting a fish count.

“I started teaching in a course last fall, called discovery science, where we focused on the future of marine fisheries and fisheries in general,” said Browne. “It occurred to me that this would be a place where we could consider a hypothetical fishery. So it served two purposes: one was to have the students have a cool project to do and two was to have a local project connected to the global topic.”

Browne and her students found low numbers of total fish and a lack of diversity within the lake. There were only about five species, and some key links in this specific ecosystem’s chain were missing. Most importantly, the fish at the bottom of the food chain were missing.

Since it is a man-made lake, the fish were probably restocked before. According to Browne, no one knows when it was restocked or with what fish. The primary fish found during the count were large mouth bass, blue gills, pumpkin seed, American eel, and catfish.

“What’s missing in that list are little fish – fish that the bigger predator fish eat,” said Browne. “So it appears that the food of the game fish, like the large mouth bass, is probably pretty low. It’s probable that they are in there, but their numbers are pretty low, if they’re even there.”

After getting advice from the freshwater fisheries division of the New Jersey Department of Environmental Protection (DEP), the next step was to receive a permit to stock the lake. Both the large mouth bass and the blue gills were restocked, and the missing forage fish – in this case, golden shiners, went in as well.

Browne and her students found that the blue gills were few in number and small in size. The DEP was able to age a couple of them from the survey, and discovered that their size was not appropriate for their age.

“We suspect they may have resorted to eating the babies, or the young of the year, of the blue gills to stay alive,” said Browne. “So that kept those numbers down and stunted them.”

The goal of Browne’s discovery science class this semester is to tag the fish. Once Rider receives the necessary permits, students will catch some of the bigger fish, tag them with a numbered plastic piece, measure them and then release them.

“Periodically we will fish more and when we re-catch those same fish, we will measure them and see if their length is increasing,” said Browne. “Over time, we might get a sense of the degree to which the fish that are in there are surviving.”

The class is working with senior environmental science major Geoffrey Scognamiglio, who took on the project for an independent study. Scognamiglio explained that so far “we have observed a good number of ‘young of the year’ or baby fish.” This find means that, although it is early in the project’s timeline, the “amount of baby fish we’ve seen in such a short timeframe looks promising for the overall population.”

On the chance the permits do not come through, Browne and her class are working on a backup plan to record the fish underwater with a GoPro camera, though the details are still unclear.

“They can swim by a scale of some sort and we can visually measure them,” said Browne. “The trick in that is we won’t know which fish it is.”

Scognamiglio added that the use of GoPros allows observation of the fish while not disturbing their natural behavior. He said they also recently had the idea to use a small boat to reach the more difficult spots.

That way, Scognamiglio said, “we will be able to fish and record video in more remote places, leaving no area unsampled and no stone unturned. Obviously fish don’t act natural when they are out of the water, so the underwater cameras will be strategically placed to watch them as they swim or feed undisturbed by human activity.”

What both Browne and Scognamiglio want students to know is that the lake’s fish population needs to be protected.

“This was not done in the hopes that we could fish someday,” said Browne. “We just figured if we have more fish in the lake it might balance out other issues, like how we have a lot of algae in the lake.”

“The more we know about the lake, the better we can do to avoid upsetting that careful balance and keeping the ecosystem in check,” said Scognamiglio. “I have always had a passion for the sciences and for fishing. It would mean the world to me to be able to leave something behind at Rider that will last for years to come after I graduate.”

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