The Rivers of Toronto: In this four-part series, the Toronto Star takes a look at the rivers of the GTA, their history, their guardians and their future.

At the mouth of the Credit River, tiny boats wait patiently in the marina for their chance to bring home the big one, an 18-plus kilogram chinook salmon.

The science of nutrient exchange from ocean to deep inland ( 1600 km in some cases ) is very interesting....

But just 50 years ago, the fish weren’t biting.

Port Credit, which now describes itself as the “salmon-fishing capital of Ontario,” had decimated its salmon stocks after years of overfishing, industrialization and pollution.

But by cleaning up the water and introducing different species of fish, the Credit River has gone from a fish wasteland to the home of a multimillion-dollar industry.

When John Kendell began the Credit River Anglers Association as an undergraduate biology student in 1993, he never thought he’d see the day when Atlantic salmon ran free through the rapids.

“We basically inherited a river that was broken,” he said. “I never thought it would look this good in my lifetime.”