As Sunday night faded into Monday, Jonathan Pierce tossed and turned at home in Roxborough, a slimy monster in his backyard keeping him awake.

Hours earlier, he had wrangled the beast out from an undisclosed location in the Schuylkill in Philadelphia. Pierce, 34, a union insulator and father of four, has hunted Pylodictis olivaris, the flathead catfish, for a decade on “the Skuke” and knew, from catching smaller flatheads, that the fish chomping down on his bait (trout head) Sunday night was simply bigger than anything he’s ever caught.

“It took off like a torpedo, running right for a rocky, snaggy section of the river,” Pierce said Wednesday morning. “It splashed its tail on the top of the water.”

Pierce’s flathead, officially weighing 56.3 pounds, will likely shatter the state record of 50.7 pounds set last spring on the Susquehanna River. It’s surely one of the biggest fish ever caught on rod and reel in Pennsylvania. Certifying a state record isn’t so simple, though. Certified scales must be used, the fishing gear documented in great detail. Sometimes, witnesses are interviewed. In some states, lie detector tests have been used, and catches have been ruled out.

“We’re pretty sure that everything appears to be good,” said Mike Parker, a spokesperson for the Pennsylvania Fish and Boat Commission.

Pierce, like most fisherman, honored the code and was vague about his exact fishing location, other than to say it was “within city limits.” That alone is rare, as most of the larger flathead catfish, considered an invasive species in the Susquehanna and all waters east of it, are usually caught outside the city.

The world-record flathead catfish was caught in Kansas in 1998. It weighed 123 pounds.

Pierce’s blow-by-blow of the catch is proof enough that fishing doesn’t mean catching, that even hooking into a fish doesn’t mean you’ll land one. He was using a 10-foot pole, something you’d normally see in the surf at the Shore. Once the fish was hooked, he knew it would swim for the rocks, to try to cut the line. Each fishing rod has a “drag” system, so that the fish can pull line off the rod, with tension. If the drag is too tight, fish snap the line. Too loose and they can take all the line off. Drag tires a fish out. Usually.

“I had my drag tight, and it was still pulling line,” he said. “Torpedo.”

Pierce’s fish got stuck in the rocks for a few minutes. He was fishing from the bank and had to wait it out. Once it was freed, the fish made a few more runs. Pierce knew it had record potential when he saw it but also knew there would be no certified scale open anywhere on the holiday weekend. Not wanting to kill the fish, he used a plastic container from home, the kind for storing Christmas decorations, to transport the 50-inch fish home. It sat in his backyard overnight, with an aerator for oxygen.

“I maybe slept an hour,” he said. “I had too much adrenaline.”

The next morning, he finally found a scale at the Blue Marsh Outdoors store in Berks County. Fish and Boat officers came to take their own measurements.

“I think it’s just a matter of paperwork,” Pierce said.

Pierce believes the flathead was at least 20 years old, and can’t imagine many much bigger in the Schuylkill. He said the next record is likely swimming in the Susquehanna. He released the fish, alive, not far from Blue Marsh Outdoors, in another undisclosed location he said was part of the Schuylkill’s watershed.