Maryland researchers investigating an unusual fish kill in June say hundreds of largemouth bass died shortly after four bass tournaments were held on the same weekend on the same 6 miles of the Potomac River.

Researchers say the kill was almost certainly related to 'delayed tournament mortality," a well-researched syndrome that kills about 25 percent of tournament-caught fish that are released with the intention that they'll remain live.

The fish die from various types of stress including several factors associated with prolonged containment in live wells. By comparison, 1 to 2 percent of fish caught and immediately released by sport anglers die from the stress of the fight.

The fishing tournament industry, including the Forrest Wood Cup, which was recently held in Pittsburgh, has greatly improved the survival rate of competition-caught bass since tournaments began growing in popularity in the 1960s. Tournament anglers holding fishing licenses from the host state are entitled to keep legally caught fish, but their goal and that of most tournaments is to put them back alive and insure that they live.

Regulation by state wildlife agencies can help, but tournament oversight among states varies greatly. Twenty thousand to 25,000 fishing tournaments are held each year in the United States. More than 1,200 of those are held annually in Pennsylvania -- Raystown Lake hosts 90 fishing tournaments per year.

The state Fish and Boat Commission keeps better tabs than agencies in many states. Here, said warmwater unit leader Bob Lorantas, tournaments with 10 or more boats are required to get free permits and file reports detailing the number of fish caught, released live and released dead. The agency sometimes helps larger tournaments to release fish, monitors the waters for dead fish, and provides tournament sponsors with guidelines -- though not enforceable rules -- on ways to increase tournament survival.

But it's an oversight and assistance role that places few restrictions on tournaments and does little to help them to keep tournament-released fish from dying. Had the level of oversight provided by Pennsylvania been applied in Maryland, it probably would not have impacted the June 29 fish kill, in which 601 largemouths and about 250 fish of other species were counted belly up in a release area shared by four overlapping tournaments. Pennsylvania rules would not have restricted the simultaneous use of waters by various tournaments, nor would they have prevented the tournaments from occurring during a period of warm water, which greatly increases stress on fish by reducing the dissolved oxygen content.

Since the high-profile fish kill, researchers with the Maryland Department of Natural Resources have studied the incident and complied a list of recommendations that tidal bass manager Joe Love suggests could help increase tournament survival rates in Maryland fishing contests.

"The reality is, you don't want to see any dead bass," he said. "Especially, local fishermen don't want to see that when tournaments come to town. There have been reports of 200 bass, but nothing like the numbers we counted. We haven't seen these numbers on record. We've never seen such a high level of delayed tournament mortality."

In an effort, said Love, "to pinpoint the causes of that [and] mitigate it in the near future," DNR prepared a report of the incident and a proposal that would overhaul Maryland's oversight of fishing tournaments. The agency took the unusual step of releasing the proposal to tournament organizers and participants, sport anglers and the media, seeking feedback.

"We have the document right now in the hands of journalists," said Love. "It highlights studies that reflect potential causes of tournament mortality and recommendations to prevent those mortalities, and some restrictions we're considering placing on release-boat captains."

The proposal, which Love described as a "direction" the agency would like to take in the next year would require all large tidal water bass tournaments to register with Maryland DNR. Release-boat live wells would have to contain at least 100 gallons of water, and would be required to measure within 5 degrees of the temperature 3 feet beneath the surface of the water outside. Angler live wells would have to include 1 gallon of water for each pound of bass, and aerated containers would keep oxygen saturation at 100 percent prior to and following weigh-ins.

"That's something a lot of tournaments get wrong," said Love. "Because of increased respiration rate due to stress, bass [in live wells, weigh-in tanks and release boats] need a high level of oxygen saturation. One hundred percent means no more oxygen can be saturated in the water. It can't hurt them. You can't put too much oxygen in the water."

Under the proposal, DNR personnel would attend all large tournaments and measure water temperatures and oxygen mixtures, collect dead fish and assist in the "design or optimization of the weigh-in procedure." Malicious negligence of those and other proposed policies would result in the cancellation of the tournament's state registration for a year, and tournament directors would have to demonstrate compliance before registration is restored.