The Toyohira River is the major tributary for Sapporo. Although it snakes its way through much of the ugly urban concrete jungle, there are often a surprising amount of anglers on the water, especially on the weekend. I’ve had moderate success landing a handful of yamame in the upper reaches, close to Makomanai Park, where the water is slowed by boulders and many large islands.
The Toyohira has wonderful, well paved, bike paths along both banks that rarely get enough use. You can cruise comfortably along the flat stretches for hours and only encounter ten to twenty other cyclists.
If you want to find the best fishing without traveling hours into the hinterland, ride south from the city center towards the Toyohira River Water Garden. It is at this point that the river starts to slow down and is more manageable for fly fishing and wading. Most of the stretches from here on can be wet waded in the summertime and will give some surprising yamame (cherry salmon) action if your willing to explore a bit.