Officers have returned to the scene of the crime, where last year they pulled up miles of illegal nets filled with 12.6 tons of striped bass from the frigid waters off Kent Island.

This year they are armed with new weapons: side-scan sonar to detect underwater nets, new laws passed by the General Assembly that expand their authority and public sentiment that has demanded a halt to poaching of the state's signature fish.

"It was just a few bad apples, but they almost ruined it for everyone," said Natural Resources Police Cpl. Roy Rafter as he prepared to board a waterman's boat Wednesday near a spot known as Bloody Point.

The commercial season began Tuesday and will continue through February. Last year, the Department of Natural Resources closed the season three weeks early while biologists assessed the potential damage caused by poaching.

The threat of closing still hangs in the air.

"If we find more nets, the possibility of closing the fishery is very real," said Tom O'Connell, the DNR's Fisheries Service director. "The General Assembly will be watching this season very closely and will not stand by and let it happen again."

No one was arrested last year, and just the thought of poachers striking once more has made honest watermen nervous.

It's not that illegal nets were new last year. In 2010, for example, officers hauled in nearly five miles of nets.

"The difference is we never found nets that full of fish," Rafter said. "Somebody knew what they were doing. It was our first time finding nets like that, but it wasn't their first time putting them there."

On Wednesday morning, Rafter and Officer James Seward nosed their patrol boat, NRP 139, away from the department's dock on Kent Island and pushed through a layer of slush before reaching the Chesapeake Bay.

Sub-freezing temperatures did not deter watermen hoping to reach their daily 1,200-pound quota. Low-slung workboats bobbed in the water as crewmen strained to haul in their nets and sort fish.

The two officers began their rounds, boarding boats to check documents and ensure that nets carried the watermen's license number and were of legal size. They inspected the catch, looking for over- or undersized fish.

This season, a new tool — Pocket Cop — has been added to their arsenal. The smartphone application allows officers to look for outstanding warrants, check a waterman's license and make sure the tags that must be attached to each fish before it is sold were issued to the waterman using them.

As they motored to the next boat, the officers looked at the sonar screen for signs of a thin white line announcing the presence of an illegally submerged net anchored to the bay bottom.

Sonar is replacing a decidedly low-tech tool: the grappling hook. Officers used to pull the hook behind their boats, hoping to snag an illegal net. The work was likened to looking for a needle in a haystack.

"The sonar shows us where to look," Rafter said. "Then we can use the hook to pull the nets up. It would have been fantastic last year."

By June 1, the DNR hopes to institute a system called "Hail In/Hail Out," requiring watermen to call the agency before leaving the dock if they want to check in their catches at the end of the day.

In addition, officers and fisheries biologists have been authorized to conduct surprise audits of the check stations, O'Connell said.

The discovery of illegal nets generated headlines along the East Coast and raised questions among regional fisheries managers about Maryland's ability to manage striped bass, also known as rockfish.