Fish Barrier Mitigation
The development of fisheries management plans for the Don and Humber Rivers in the 1990s identified in-stream barriers as one of the limitations to the health of the aquatic community. Mill dams, weirs, and in some cases, roads and culverts, considerably reduce the ability of many fish species to move freely within each watershed and to access spawning areas. Migratory rainbow trout and chinook salmon were only able to access the lower 3 km of the Don and Humber Rivers and due to environmental conditions in these areas, spawning was unsuccessful.
More than ten barrier mitigation projects have been completed in rivers within the TRCA's jurisdiction in the past four years. Three different designs - rocky ramps, Denil fishways and notching - have been used to achieve fish passage in these projects.
Follow-up monitoring of these projects had already shown significant results. In 2000, rainbow trout were found in the East Humber River more than 30 km upstream from Lake Ontario; chinook salmon were seen in the East Don River more than 20 km upstream from Lake Ontario. It is anticipated that successful reproduction in these recently accessible areas will result in self-sustaining runs of these popular sport fish. The presence or absence of juvenile trout and salmon will also be useful in assessing the health of these watersheds.