A University of Guelph study has discovered where endangered redside dace fish go during the winter as well as their sensitivity to pollutants like road salt.
The small redside dace are an important part of the local food web because they hunt and eat terrestrial insects while also being a food source for bigger fish, said Jaclyn Cockburn, associate professor of geography at the University of Guelph.
In Canada, the redside dace is found only in a handful of tributaries along western Lake Ontario, Lake Erie and Lake Huron. Because the fish is so sensitive to degraded habitat and water quality, it has become rarer within southern Ontario in general and the Toronto region in particular. A 2007 study uncovered information on where redside dace tend to live in the warmer months, but it wasn’t until early 2014 that a study got underway to find their winter homes, which would be useful information for fishery management and developing conservation and restoration plans.
This posed issues that project lead (and former grad student) Lindsay Davis had to resolve.
The streams freeze over in the winter, and because the redside dace is endangered, electrofishing isn’t allowed. The streams also are too small for scuba or snorkeling work – which is not advisable in the winter. So part of Davis’ work involved figuring out a viable way to track the fish, settling on placing small waterproof cameras in the water for 30-minute intervals; results from this approach were published in the Journal of Freshwater Ecology in 2016.
The study looked at several streams in the Toronto region, including restored streams and those in conservation lands that have been largely untouched, with multiple locations within each stream.
Researchers found that in the winter, redside dace prefer to find areas with woody debris – comprised of parts of trees that either have grown or fallen into the water – as this provides the fish with ample hiding places and cover from predators that terrestrial insects tend to stay near.
While they are strong swimmers, Cockburn said, redside dace don’t like to go far if they don’t have to. The fish seem to avoid areas predominantly made up of cobble stones or aquatic vegetation. In the study, it didn’t seem to matter if the stream was restored or natural. As long as the proper habitats existed somewhere in the waterway, redside dace tended to gravitate there.
Moreover, redside dace avoided areas where the degree of dissolved salt was “off the charts,” Cockburn said.
Those high readings were likely a result of road salt washing into the waterway, and the redside dace appeared sensitive to this particular pollutant. This can be problematic in the winter, as the areas where water temperatures stay in the dace’s ideal range also can be places where dissolved salt washes into streams. Cockburn noted that the species’ winter habitat is more fragmented than it is in warmer weather, notably due to lower water levels in the winter and ice cover.
While fieldwork wrapped up in 2016, Cockburn said final results from the study are still awaiting publication in a scientific journal.
Looking ahead, she said the research team is interested in looking at streams on the eastern side of Toronto, which notably have more beaver dams than the streams previously investigated.
Beavers tend to move into stream restoration sites, and when they colonize an area fish species tend to follow quickly. She said researchers would like to investigate whether redside dace are one of those fish species that are expanding their range as beavers return to these streams.