Duffins Creek - Toronto and Region Conservation Authority

4Duffins watershed (Table 1). Included in this listare nine non-native species: sea lamprey, rainbowtrout, brown trout, coho salmon, chinooksalmon, alewife, goldfish, white perch andcommon carp. Although non-native, the troutand salmon species are considered by some to bedesirable from a recreation standpoint. At onetime trout and salmon were stocked in the creek;presently only brown trout are still beingstocked. Atlantic salmon is the only knownextirpated species once found in Duffins Creek(ODPD, 1956). The creek is currently being usedby the Ministry of Natural Resources to researchthe habitat requirements and to evaluate thefeasibility of restoring Atlantic salmon to LakeOntario tributaries.In the 2000 survey of the Duffins fish community,28 species were encountered (Table 1). Thisincluded three non-native species: chinooksalmon, rainbow trout and brown trout. Thefewer species found in the 2000 survey is likely areflection of the decreased extent of sampling,the sites selected for sampling and possibly somespecies losses. Coldwater streams in the upperand middle reaches of the Duffins Creekwatershed provide habitat for species such asbrook trout, and slimy and mottled sculpin.They also provide habitat for species at risk suchas redside dace (Clinostomus elongatus). In thelower reaches of the west and east Duffins Creekthere is coldwater habitat that supports ahealthy, self-sustaining, rainbow trout population.It is also likely that chinook and coho salmonspawn successfully in the lower reaches. Thesespecies of salmon and trout are separated fromthe native brook trout populations by several instreambarriers that prevent the upstreammovement of migratory species. Previous studieshave shown that the non-native salmon andtrout would out-compete the native brook troutif their distributions were allowed to overlap.According to the MNR District FisheriesManagement Plan 1989-2000, the DuffinsCreek watershed supports primarily brook andbrown trout in the headwaters and migratorysalmonids below Highway 7. Most of thewatershed is considered coldwater habitat withthe exception of Stouffville Creek, and the lowerDuffins below Highway 401. Stouffville Creekonce was coldwater habitat, but now it iswarmwater because of the presence of theStouffville reservoir, an online pond, and a lack ofwoody riparian vegetation to shade the stream.Conversely, the lower Duffins Creek is a naturalwarmwater reach. This a consequence of the sizeof the creek and the low quantities ofgroundwater input into the creek at this locationin the watershed. The lower Duffins andassociated marsh provide good habitat for anumber of warmwater species such as smallmouthbass, northern pike and pumpkinseed.The ecological health of a fish community can bequantified through the calculation of an index ofbiological integrity (IBI). The IBI figuresquantifies the ‘health’ of the fish community byincorporating species richness, trophic balance,the abundance of fish, and the presence ofindicator species into one index. This method wasfirst proposed by Karr (1981) and was furthermodified and calibrated for southern Ontariostreams by Steedman (1988). Interestingly,fisheries information from the Duffins watershedwas used by Steedman to calibrate the IBI forsouthern Ontario streams. More importantly, hefound that many (77 per cent) locations in thewatershed had good to excellent fishcommunities (Figure 1).Surveys from the 1990s found similar conditions,which is expected, because there have been fewchanges in the watershed that would impact thefish community. Overall, analysis of the watershedfrom the 1950s to the 1990s has demonstrated ageneral increase in the number of species and thedistribution of trout species (Jones and Guy,1997). The 2000 survey of 32 sites in the Duffinsresulted in IBI scores from fair to excellent, witha median score of good (Figure 2). This is a goodresult given that a high percentage of the sitesscored good (53 per cent), three were excellent (9per cent) and no sites were in poor condition orhad no fish present (Figure 2).