You make your way to your favorite stream, ready for a day of leisurely fishing. You soon find out that there's just one thing missing. Fish.

What could be wrong? The preliminary results of a study by University researchers indicate that the problem might be the aluminum concentration in the water and that acid rain could be to blame.

Funded by the Environmental Protection Agency, faculty and graduate students from the School of Forest Resources and the graduate programs of ecology and environmental pollution control have been studying five streams in southwestern Pennsylvania since fall of 1988 to learn more about the relationship between aluminum in the water and the death of fish.

"Previous research by others has established that aluminum affects the permeability of the gills and (the fish) lose salts, especially sodium. They get down to a certain percentage of body sodium, they can't recover, and they die," said David R. Dewalle, project coordinator and professor of forest hydrology.

Bob Carline, co-investigator of the project and adjunct associate professor in the School of Forest Resources, described the study as having both chemical and biological elements. Chemically, the researchers are trying to characterize the nature of high-aluminum periods in the streams as to their frequency, severity and duration. Biologically, the researchers are determining how the fish respond to these episodes.

The researchers use various methods of surveying the fish, such as electrically stunning them or implanting them with transmitters and tracking them. At the same time, other researchers monitor the flow rate, the acidity and the aluminum concentration of the streams.

They have found that the aluminum concentration in the streams varies widely, peaking during spring runoff and after heavy storms. This is when stream conditions are toxic to the fish.

"The interesting thing about the way this aluminum concentration varies is it only gets high during these periods of high flow which don't occur that frequently," Dewalle said.

The aluminum found in streams comes from the surrounding soil and dissolves into water that comes into contact with it. The amount of aluminum dissolved increases with the acidity of the water.

"What we think is happening is that acid rain could be increasing the acidity of the soil water . . . and that allows more aluminum to be dissolved in the soil water and that water, especially during the high runoff periods, becomes stream water," Dewalle said.

The streams that were chosen for the study were considered at risk from high aluminum levels and had brook trout populations ranging from well-populated to almost devoid of fish. Brook trout were chosen as the focus of the study because the species is the major native trout in the streams and has a relatively high aluminum tolerance.

Carline believes that an understanding acid rain's effect on aquatic life has been reached.

"We've shown a direct link between atmospheric deposition and toxic conditions in the streams. . . . The bigger problem we're facing now is whether the government will take actions to reduce emissions," he said.

Lately, though, federal government attention (and funding) has begun to shift to other environmental problems such as ozone layer depletion and global warming, he said.

"Our government has a short attention span when it comes to scientific issues like this . . . Without politics interfering we probably would have had at least some reasonable increase in atmospheric pollution reduction in this nation long before now," Dewalle said.

Part of the reason for the delay in enacting more stringent pollution controls has been the cries from industry for more proof of the detrimental effects of acid rain, he said.

It is true that in many cases researchers lack the historical data needed to prove that a change for the worse has occurred, he added.

Because of the lack of other data, the researchers had to use Fish Commission records that showed that some streams could no longer be stocked because the trout would die before the first day of the fishing season, Dewalle said.

Some of these streams were being polluted by obvious sources such as run-off from nearby coal-mining operations. It was the streams that had no easily recognizable pollution source that became the focus of this study, he said.

"(The lack of data) is part of the reason why this acid rain controversy has existed for so long, that's why it's taken the U.S. so long to try and enact more stringent pollution-control legislation," Dewalle said.

"If you stand back and look at the acid rain issue, I think there are some lessons here . . . there is a definite need for long-term monitoring of the status of our natural environment so that we can detect a change," he said.