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Start of Trout-Fishing Season Highlights a Complex, Years-Long Process at Benner Spring and Other State Hatcheries

This story appears in the April 2021 issue of Town&Gown.

On Saturday, many anglers will ready their fishing rods for the start of Pennsylvania’s trout season – a season largely made possible through the work of state fish hatcheries.

State College’s Benner Spring Fish Hatchery Manager Doug Hess is hoping this trout season will offer a little bit of normalcy for anglers, despite the ongoing pandemic that posed challenges in scheduling events and hatchery operation last season.

“We just started [our work] earlier to make sure that we had the time-frame needed to get all fish in prior to April 3, so that we can have a traditional opening day even though it’s a little different than what it’s been for decades,” he says of the earlier-than-usual, single statewide opening.

The process of raising trout at the hatchery is complex.

A years-long process

Typical stocked fish are 16-18 months old, Hess says. The typical trout hitting the waters this spring were spawned in state hatcheries in the fall of 2019. Three-year-old females used for egg collection are stocked in state waterways as trophies the following season.

The first step to raising healthy fish to stock in Pennsylvania waters is spawning the fish. According to Hess, Benner Spring workers do this job by hand.

The female fish are put to sleep with an anesthesia-like chemical, so workers are able to safely apply pressure to the fish’s abdomen, which causes her to release eggs. The same process repeats with the male fish to get the sperm. Both the sperm and the eggs are then mixed by hand to fertilize the eggs, Hess says. The fish recover unharmed in a few minutes once placed back into fresh water.

Eggs are then put into incubation trays where, after a certain amount of time – about three weeks for rainbow trout – workers are able to remove any unfertilized eggs from the trays, moving the young fish into their first series of tanks. In these tanks, Hess says fish are called “sac fry,” because each fish has a yolk sac it feeds from, and workers will clean up egg debris.

Fish are then moved back to the incubation trays. Then, after about three more weeks when the sacs are gone, fish will be placed back into the tanks where they’ll be fed by workers. Fish here are called “swim-ups,” as they start to move to eat food from the top of the water, and then “fingerlings,” as they grow to be the size of fingers.

Depending on the hatch rate, the hatchery has about 1.2 million to 1.5 million fish in the swim-up or fingerling categories, Hess says. As the fish grow, they are moved into appropriate-sized tanks. The hatchery houses about 70 rearing tanks used to raise and store different kinds of trout throughout their early lifecycle, Hess says.

Eventually, fish are moved outdoors to 500-foot-long raceways, which act as in-ground tanks for the older fish. Hess says the hatchery is able to produce 500,000 adult trout, which are kept and fed in these raceways until they are transported and stocked into Pennsylvania waters throughout trout season.

Outdoor raceways serve as in-ground tanks for older fish, being fed by Greg Hartle. Photo by Darren Andrew Weimert | Town&Gown

Clean tanks, healthy trout

The fish are kept in tanks that can house about 50,000 each, so it’s important to consistently clean and monitor for any kinds of diseases, Hess says.

“Because we have a lot of fish, it’s like a classroom of kids,” he says. “One gets sick, they all get sick.”

To ensure fish are healthy, the tanks are cleaned every day and the hatchery has two on-site biologists who make up the “fish-care unit.” Benner Spring has one of the highest qualifications in the state, Hess says, meaning that the fish raised there are consistently healthy enough to send out to other hatcheries if needed.

“Benner Spring has a little bit of an added emphasis on [fish health], so we actually do more than we are required to do ourselves, because we know that other facilities may have an issue that occurs, and they’ll request additional fish from us,” Hess says.

Hatchery workers keep logs of the fish that die while in the tanks, to watch out for any trends that might indicate a bigger problem, he says. There are also other telltale signs of sickness, he says.

“They’re just like any other animals, even people. If you’re sick, you’re not hungry,” Hess says. “These are rainbow trout. If you put feed into these and they don’t eat, there’s something wrong with them because they’re little pigs. They love to eat.”

If there does appear to be a trend in mortality, hatchery biologists will take samples to figure out the problem, he says.

Workers at the hatchery, including Richard Campbell, clean and monitor tanks to ensure fish are health. Photo by Darren Andrew Weimert | Town&Gown

What about the water?

Running a fish hatchery requires a lot of water – and for the Benner Spring hatchery, much of that water comes from Benner Spring, hence the hatchery’s name. It’s not as simple as just filling a fish tank once, however. To survive, trout need to have a constant flow of fresh water.

“Here at the trout hatchery, it’s like a stream, because everything’s constantly flowing through,” Hess says.

All the water used by the hatchery is sent to its filtration building, which has three drums with 256 filter panels each. These filter panels have mesh that is 20 microns in size so only the tiniest of particles can pass through them. This process is one of the most important roles of the hatchery, as every drop of water used will pass through those filters, which are monitored for proper function and any needed repairs, Hess says.

“We work daily to make sure that the building is maintained and that everything is being filtered correctly” he says.

Waste has been greatly reduced at the facility through the years, Hess says.

Once the water is filtered, some of it is recirculated back into the hatchery, while the rest is discharged into Spring Creek.

“I’m really happy to say that … we haven’t had any issues here for quite some time. For most part, [the water is] as clean going out as it was coming in. A lot of times it’s cleaner,” Hess says.

This process allows the hatchery to take less water from local springs, while also discharging more clean water back into the streams.

Mark Jackson, of Warriors Mark, removes a rainbow trout from a float used to stock trout on Bald Eagle Creek. Photo by Darren Andrew Weimert | Town&Gown

Shifting demands

In 2020, the Pennsylvania Fish & Boat Commission stocked state waters with about 3.2 million trout. Of that amount, 14,352 were golden rainbow trout – a novelty for the Pennsylvania angler.

“They’re out there for the angler to get a fish-of-a-lifetime kind of a thing,” Hess says.

As the hatchery manager, Hess says his job is primarily concerned with the recreational aspect of hatcheries. And that means listening to the wants of the anglers who are out on the water, trying to catch these hatchery-raised trout. But the process to decide what kind of fish to stock, and how many, is ultimately up to the biologists, he says.

About a decade ago, Hess says, anglers requested that the trout be larger in size. Fulfilling anglers’ requests is a balance, though. With the requests for bigger production trout, the hatchery has to consider the amount of waste these bigger fish would produce and the amount of feed needed to sustain them. In order to satisfy the anglers’ requests while adhering to the biologists’ advice, Hess says the hatcheries came up with a kind of compromise: providing larger trout, but fewer of them.

But also at the request of anglers, there are more trophy fish.

“We’ve increased by threefold the number of trophy fish that we’re actually putting out in the water for the anglers,” he says. “It takes our biologists and it takes our commissioners and it takes our fish wardens and the hatcheries all working collectively together to agree on, ‘Yes, this is the right direction to go. This is what the anglers want. So here you go, we’ll do it.’”

Since 2007, PFBC trout hatcheries have been stocking about 3.2 million adult trout that are around 11 inches and weigh more than a half pound each. In 2021, the PFBC has increased the number of trophy-sized trout to more than 70,000.

But fish hatcheries don’t just hear from anglers. Conservation groups also weigh in.

The Spring Creek Chapter of Trout Unlimited advocates to ensure all cold-water streams have high protections, which would eliminate fish stocking in them, according to chapter President Jamie SanFilippo.

However, SanFilippo says there are benefits to connecting the public with trout fishing, as it often can foster connections between individuals and conservation.

“Trout fishing can turn recreational anglers into passionate conservationists and fly fishermen, who want to give back to the resource they appreciate so much,” SanFilippo says. “Conservation and trout fishing must go hand-in-hand to ensure the preservation of the beautiful environment that wild and native trout rely on to survive.”

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For more information on fish hatcheries or trout stocking schedules, visit For more on the Spring Creek Chapter of Trout Unlimited, visit