Barrie Creeks, Lovers Creek, and Hewitt's Creek Subwatershed Plan

The Barrie Creeks, Lovers Creek and Hewitt’s Creek Subwatershed Plan
A general overview of the current fish communities is looked at first to see what type of fish are
at a site (cold water species 1 , warm water species 2 , or no fish) and what the temperature of the
creek is at the site (cold, cool or warm water), as well as the location of dams that block
passage for some fish species (Figure 5-2). This broad overview can show the general shifts in
the fish communities as coldwater fish communities either change into warm water fish
communities or habitat absent of fish, as water temperatures rise or where dams are present.
Figure 5-2 shows that temperature varies along most of the watercourses. Despite this, cold
water species, such as brook trout and mottled sculpin, can be found across all three
subwatersheds. There are also a number of sites that either have only warm water species or
no fish species at all. The dams depicted on the map also show where the major barriers to fish
are located.
There are a few anomalies where cold water species are found within warm water habitat or
warm water species in cold water habitat. The most likely reason that cold water species are
found in warm water habitat is that there are small nearby temperature micro habitats, such as
undercut banks and heavily shaded areas with cold water upwellings, springs or seeps. It is
also possible that a species was passing through or leaving the warm water habitat at the time
of sampling, but this would be more unusual. Warm water species are habitat generalists and
can exist in warm, cool or coldwater conditions.
An Index of Biotic Integrity (IBI) was used to assess the ecological integrity of the creeks
through the composition of fish communities within the system (Figure 5-3). Fish population and
community composition surveys are valuable tools in examining the health and stability of
streams and rivers. Over time, shifts in composition along with the presence or absence of key
species not only provides an indication of system health but can be used to help identify what
ecosystem stressors, such as climate change and urbanization, are influencing aquatic habitats.
With this method there are five rankings that can be assigned to a site:
• Very good: Excellent diversity, top predators, trout present and high fish abundance
• Good: Average diversity, top predators present, trout present, average abundance
• Fair: Low/average diversity, some top predators, no trout, low/average abundance of
fish
• Poor: Low diversity, no top predators, no trout, low abundance of fish
• No Fish: No fish were captured at these sites
While the IBI is generally applicable to the Lake Simcoe watershed, there is potential for
improvement by including a greater range of top predators into the IBI calculations. Currently
only brook trout are weighed and measured individually. This may skew the results as warm
water predators are not included in the IBI calculations.
Overall, Figure 5-3 shows that the ecological integrity of the systems vary spatially across the
subwatersheds, with many of the sites showing fair conditions. There are also several ‘good’
ratings in each of the subwatersheds, as well as a number of sites that were rated as having
poor ecological integrity. It is also important to note that all headwater sites within the Barrie
Creeks subwatershed had no fish captured.
1 Cold water species are indicators of cold water habitat. Coldwater species found in these subwatersheds include:
rainbow trout*, brook trout, rainbow smelt *, mottled sculpin and slimy sculpin (*not native to Lake Simcoe
watershed). All others listed in Table 5-2 are either cool or warm water species.
2 Warm water species are considered to be generalist species that are not coldwater indicators and can exist in warm,
cool and coldwater sections of a stream.
Chapter 5: Aquatic Natural Heritage 211