After many years of disease and depressed populations, smallmouth bass have recovered somewhat in the Susquehanna River, enough so that Pennsylvania regulators are looking to ease a spring fishing ban that has been in place since 2012.

The state Fish and Boat Commission is considering reopening the spring smallmouth spawning season, which for the last five years has been closed to anglers from May 1 to June 18 along 98 miles of the middle and lower Susquehanna and 32 miles of the lower Juniata River, a major tributary.

The proposal, to be taken up at the commission’s July 10 meeting, has sparked almost as much controversy among anglers as the original closure.

“Fishing during the spawn is like fishing in a stocked pond of trout — it’s not OK,” said Barry Potteiger, founder of the Susquehanna River Bassmasters Club in Harrisburg.

Imposed in 2012, the ban followed catch-and-immediate-release regulations a year before. Both regulations are in response to a high percentage of diseased fish and widespread die-offs dating back 2005 in those sections of the rivers. Under the commission’s proposal, anglers could catch and release smallmouth bass during the spawn. Tournaments are still banned while bass are reproducing but are allowed the remainder of the year — with catch, measure and immediate release restrictions.

Anglers who want to keep bass will have to fish in the upper Susquehanna and Juniata or a different waterway. Streams and rivers outside of the area are open to harvest fish, including tournaments during bass season.

Smallmouth bass in the Susquehanna and other waterways in the Chesapeake Bay watershed, including the Shenandoah and Potomac rivers, have suffered fish kills linked to disease and parasite infections. While no definite cause has been found, federal and state scientists suspect herbicides and other chemicals could be suppressing fish immune systems and leaving them vulnerable to pathogens.

But according to annual commission surveys, the prevalence of disease and parasite infections has declined in recent years. Biologists sampling the river with electrofishing gear have seen nearly four times as many large bass in the middle Susquehanna in the last decade than they did in the previous 10 years.

John Arway, the commission’s executive director, said the fishing restrictions have helped large fish rebound, as have favorable weather and river flows. But he stressed that while the population of juvenile bass has increased, it is not what it was before 2005, and that the Susquehanna River is still sick. Arway and the commission have tried unsuccessfully to have the river designated as impaired and put on a pollution diet, much like the Chesapeake Bay. The Department of Environmental Protection has said there isn’t enough data to support that action.

“I’m as conflicted as everyone else,” Arway said of the proposal to relax the bass spring fishing ban. “We can have a repeat of 2005 in a minute.”

The ban on fishing during spawning season was intended to protect large bass so they could reproduce. At the time, spawning was hit or miss, said Geoffrey Smith, a commission biologist.

“They could have one good year, then two or three bad years,” Smith said. “We weren’t getting any of the good years until the past two or three years.”

Now, he noted, more young bass are surviving to reach their first birthday. The decline seen in disease could be the cause. In the mid– to late 2000s, evidence of disease was found in 50–70 percent of fish less than a year old that were caught during annual electrofishing surveys. That incidence has declined to 10–25 percent in the last five years.

For years, scientists have been finding bass in the Susquehanna and other Bay region waterways with a blotchy skin disease, viral and bacterial infections and parasites. Researchers suspect the maladies are linked to chemical compounds in the water.

Though signs of disease in fish may be down, federal and state scientists said that sampling of water and fish tissue continues to detect agricultural and lawn care chemicals, as well as pharmaceuticals used in humans and livestock. Some of the contaminants found are considered endocrine disruptors, which interfere with hormone systems. Such chemicals could be causing a condition known as “intersex,” they suggest, in which male bass carry oocytes or egg precursors in their testes.

“What we are trying to figure out is why these young fish, about 2 or 3 months old, contain such high loads of different types of parasites,” said Vicki Blazer, research ecologist with the United States Geological Survey’s Leetown Science Center in West Virginia. “To me, that means the fish are immuno-suppressed.”

Still, while individual fish may be sick, the population appears healthy right now, said Smith, the commission biologist. And a review of studies made elsewhere indicates that fishing during the spawning period doesn’t negatively affect overall abundance, he said.

Recreational anglers generally agree that bass have come back in a big way in the past few years, but they’re divided over whether the recovery is strong enough to ease the restrictions.

Some say the Susquehanna population is so robust now that the year-round catch-and-release requirement should be dropped, letting them keep what they hook. But roughly three quarters of those who weighed in on the issue want to keep the spawning season closed, Smith said.

Potteiger, the Harrisburg bass club founder, opposes opening the spawning season, a proposal he contends is intended mainly to benefit commercial fishing guides.

He said he thinks the commission ought to consider easing the catch-and-release restriction instead. If the fishery is healthy enough to open the spawn, he argued, then it should be healthy enough for the “average Joe” to keep a fish or two.

Many commercial fishing guides do support reopening the spawning season, because it has been a prime time for clients, who want to get out in spring.

“The fish commission wanted to present their case and brought five guides in to discuss it,” said Rod Bates, a longtime Susquehanna fisherman and professional guide. “One found the river had never been worse, the others found the river had never been better. I was the middle of the road.”

Bates, though, said he would like to see catch-and-release restrictions not only maintained, but extended to other Susquehanna tributaries. Maintaining the adult population in tributaries could contribute new fish to the river. Without that kind of added protection, he predicted, an open season during the spawn will hurt the population.

“If you open up the river, and don’t protect the tributaries, I can assure you, you’re not keeping the fish.”

In any case, Bates said, something has to be done, because some anglers are cheating on the spawning season ban. During a recent taping for a local outdoors television show, Bates recalled that he saw two boats carrying bass gear launch a little more than a week before spawning season was over.

“I’ve been keeping watch to see how many are out fishing here,” he said. “I really believe that if you’re going to close it, let’s consider putting out some more enforcement.”