More than a quarter of the lakes studied in upstate New York's Adirondack Mountains are so acidic that they contain few fish if any, concludes a study on the effects of acid rain that was released Friday.

Shallow lakes in the southwestern Adirondacks are the most susceptible to high acidity, according to the study by the Adirondack Lakes Survey Corp., a company formed by utilities and state environmental officials.The survey of 1,723 lakes, mostly in the Adirondacks, is the most comprehensive ever done to examine the effects of acid rain, said James Mahoney, director of the federal Acid Precipitation Assessment Program.

"This whole acid rain phenomenon is so complicated that it's a great help when you see a big mess of data that confirms your natural speculations," Mahoney said.

Much of the contamination of New York state lakes can be traced to sulfur dioxide emitted from factories in the Midwest and borne by prevailing wind to the north and east, said Charles Driscoll, a civil engineering professor at Syracuse University.

But since many lakes in the Adirondacks are naturally acidic, it's premature to conclude that the blame for all the damage can be traced to Midwest factories, Driscoll said.

Of the 1,469 lakes surveyed in the Adirondacks, investigators found no fish in 346 and fewer than 10 fish in 79. That's 29 percent of the total.

The survey found that 352, or 24 percent, of the lakes studied had pH levels of 5 or below. The pH level is a measurement of acidity. Anything below 5 is considered unlikely to support life.

But in the southwestern Adirondacks, 40 percent of the lakes have pH levels of 5 or below.

Environmentalists had some good news. The survey examined 254 lakes in New York's lower Hudson River Valley and Catskill Mountains, south of the Adirondacks, and found only 3 percent with pH levels of 5 or below.

"Generally, the conditions there are excellent," said Walter Kretser, project manager of the survey.