Though summer can be murder on trout, smallmouth bass and walleye also are getting whacked by this year's hot, dry weather.

Cooperative trout nurseries across Pennsylvania have lost 50,000 rainbows, brookies and browns destined for stocking. On the Susquehanna River and its tributaries, including Penns Creek and the Juniata River, smallmouth bass have gone belly-up in big numbers. And at Pymatuning, scores of dead walleye have been seen floating on the water.

Fish commission biologists blame warm water and low flow -- a combination that can be lethal to trout, a cold-water species, in the wild. But this is not usually a problem for walleye and bass, which can tolerate higher temperatures.

On the Susquehanna, about half of the young smallmouth bass have been infected with the common bacteria columnaris, which attacks gills and causes skin lesions. Though the fish commission blames water conditions, longtime river users cite pollution, a factor the commission has downplayed but not ruled out.

Still, the Susquehanna has been cited by the conservation group American Rivers as the most endangered river in the nation because of the effects of municipal waste and agricultural runoff.

Bob Clouser, a longtime Susquehanna River bass guide and creator of the Clouser Minnow fly pattern, believes waste from hog and chicken farms, lawn care chemicals and other toxins have reduced dissolved oxygen levels in the water to the point where they are suffocating fish.

"The quality of the river has been going downhill in the last seven to 10 years. It's a very serious situation that people need to stand up for," he said. "Catch rates were 60 per boat a few years ago and now they're down to five a day.

"Hot weather may be contributing, but it isn't the main problem. And you can quote me on that. Nobody in state government has the nerve to tell you."

Hatcheries feeling heat

Columnaris spawned by warm, low water is more often associated with hatchery trout -- given that fish are in close quarters -- and it is taking a toll on fish being raised this summer at many of the 180 cooperative nurseries owned by sportsmen's groups across the state. So far, 50,000 trout being raised for public lakes and streams have died, according to the fish commission's Steve Archer.

State-owned hatcheries, which grow most of the 4 million trout the commission stocks each year, are so far unaffected because they are situated on spring-fed or limestone streams that maintain good flow and temperatures, said Leroy Young, the commission's fisheries management division chief. But many cooperatives are on waterways of marginal quality, which makes trout more vulnerable to disease under extreme conditions.

"This is the worst [die-off] we've seen in years," Archer said.

The fish now dying were just given to the co-ops by the commission and measure up to 7 inches. Archer said raceway water has been salted to try to relieve stress on fish and control bacteria, and antibiotics have been added to fish feed.

"I think it'll slack off with rain and nights with cool temperatures," he said. "But that won't be until mid- to late August."

According to AccuWeather senior meteorologist Henry Margusity, this summer might feel like a record breaker, but it isn't.

"It just feels hotter because there's so much humidity. It started in June and has stuck around, with so few cold fronts to bring relief," he said. "Precipitation has been just slightly below normal, except for central Pennsylvania through the northeast, where it's at about 50 percent of normal, although thunderstorms have been more isolated."

Walleye getting walloped

Heat is being blamed for the walleye die-off at Pymatuning, where adult, large-size fish have been found floating in recent weeks. However, no fish had been collected for evaluation as of July 28, according to Bob Lorantas, the agency's top warm-water biologist. The phenomenon has longtime users of the reservoir scratching their heads.

"I saw a dozen walleye floating between the causeway and Orchard boat launch," said Jim Scalise of Bethel Park, an angler who owns a cottage on the lake. "I've been fishing Pymatuning for 30 years and I've never seen a dozen fish floating dead like that. One was 30 inches."

According to Lorantas, water temperatures are stressing walleye and the shallowness of the reservoir is offering them almost nowhere to go for relief.

"Eighty-five degrees isn't necessarily a temperature that would cause problems for walleye," Lorantas said. "But lakes stratify in summer, and in a lake this shallow, there's little opportunity for walleye to find cooler refuge."

Some anglers have questioned whether herbicides used for vegetation control could be a culprit, but the Pennsylvania Department of Conservation and Natural Resources said it hasn't applied any chemicals this year.

"It seems a little strange to me, to tell you the truth," Young said of the die-off. "We seem to see mortality of one species around spawning time. That's not uncommon. This is a little more uncommon. There are virus-type diseases that can affect one species, more so when they are under stress."