...	Herald Photo A dead fish lies in brackish water in the Little Sackville River near Sackville Crossing Road on Sunday.

By Susan Bradley / Staff Reporter

A Halifax environmental scientist believes a toxic substance was introduced into the Little Sackville River, killing nearly all the marine life for a three-kilometre stretch.

"I have been studying the sediment in this river for two years," Cathy Conrad, a geography professor at Saint Mary's University in Halifax, said Sunday.

"Sediment or silt alone would not have caused that to happen, even if it was a massive amount.

"And the odour. There absolutely had to have been something of a chemical nature" in the water.

The substance, so far unidentified, entered the river sometime overnight Thursday.

By Friday morning, hundreds of fish, including a large number of baby Atlantic salmon, were dead.

Ms. Conrad's water samples are among those being analysed by the provincial Environment Department. She visited the river on Saturday.

The analysis is taking place under stringent conditions so it would stand up in court if criminal proceedings are warranted, Ms. Conrad said.

Dr. Maureen Baikie, the associate provincial medical officer of health, denies there are any chemicals in the river that may be harmful to humans.

After consulting with Environment Department investigators, she decided not to issue a public health advisory warning people to stay away from the river.

"My understanding is that the cause is most likely a water main break that stirred up silt and other materials on the bottom of the river," she said.

"That, combined with low water levels and high temperatures, stressed the fish and they died."

Ms. Conrad isn't convinced.

"I know she (Dr. Baikie) is just going on information she has been given," she said. "But until we know what is in the river, I don't think people, especially children, should be playing in it or touching the dead fish."

"I wouldn't put my finger into the water," said resident Dawn Smith of Lower Sackville. "I even was hesitant with gloves.

"I have been chasing children away from the river all weekend."

Ms. Smith, whose property borders the river, said Sunday the chemical odour is still strong.

One theory, Ms. Conrad said, is the contents of a holding pool behind Downsview Mall may have overflowed, sending parking-lot runoff, including oil, gas, salt and other substances, into the river.

Whatever caused it, the damage to the 11-kilometre river, the main tributary of the Sackville River, has been massive, said Walter Regan, president of the Sackville Rivers Association.

Over the past 14 years, the association, with about 100 volunteers, has reforested the riverbank, stopped the erosion and siltation, limed the water and restored fish habitat. The project cost more than $500,000, Mr. Regan said Sunday.

Each spring, elementary school students have been releasing salmon fry they raise from eggs into the Little Sackville River as part of the Atlantic Salmon Federation's Fish Friends program.

Mr. Regan has been monitoring the damage since Friday and in a one-kilometre section has counted over 500 dead fish, including salmon, American suckers and eels.

"I am absolutely livid," he said. "The stuff has sunk to the bottom today. It's the colour of a Tim Hortons double-double at the top (of the river) and grey farther down. Someone has to take responsibility for this."

The damage could get worse if a heavy rainfall drives the substance downstream to other parts of the river, Ms. Conrad said.