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Ken W. Watson

Note: This articles first appeared in the Spring 2001 edition of Rideau Reflections, the newsletter of the Friends of the Rideau.

At the 2000 fall meeting of Friends of the Rideau, three speakers from the Canadian Museum of Nature gave interesting talks about some of the results of the Rideau River Biodiversity project.

Fish in the Rideau
by Claude Renaud

Dr. Renaud introduced the Rideau River Biodiversity project, which was a three year project, running from 1998 to 2000. The project investigated many aspects of the Rideau River, concentrating on the area from Merrickville to Ottawa, but also encompassing areas as far south as Big Rideau Lake.

A core part of the fish study is the Master’s thesis of Ann Phelps. It set out to see if there was a difference in the fish fauna between areas of urban, agricultural and natural landscapes. The main study area included 14 sampling sites between Merrickville and Rideau Falls (Ottawa).

Fish were caught using various means, then measured, weighed and the habitat in which they were found described. During the course of the study, some 6900 fish were checked, representing 30 species. The breakdown of habitat diversity showed 22 species in areas adjacent to forests, 25 adjacent to urban areas and 28 adjacent to agricultural areas. In terms of total number of fish collected, about 50% came from agricultural areas and the lowest number came from urban areas. A literature study was also done to investigate the historic research regarding fish species diversity. It was noted that there were several introduced species in the Rideau, an example being Walleye that was introduced in the 1930s. The fish population is quite healthy. Some fish show black spots but these are not a disease, they are a result of snails attaching themselves to the fish. Of note are deformed rib cages of many smallmouth bass. It is unknown if this is habitat or genetically related. Documentation of this deformity dates back to 1959.

In terms of future health, the team picked a small fish, the Brook Silverside (Labidesthes sicculus) to act as a sentinel species. The choice of sentinel is a fish that is abundant throughout the study area (i.e. easy to catch) and mid-sensitive to environmental conditions.

Amphibians on the Rideau
by Francis Cook

Dr. Cook started his talk by showing newspaper headlines about frogs disappearing, with speculation that this related to environmental degradation. He noted that there is no scientific foundation for this assumption; the jury is still out on the causes of frog species decline in several parts of the world. Habitat loss may be a more profound cause than environmental degradation. He also noted that climactic change is not a new phenomenon, if we look back a few hundred years and a few thousand years, we see great fluctuations in global temperature.

In terms of our region, continental ice sheets covered the land until about 13,000 years ago. It is safe to say that all amphibians came into our area after the glaciers receded. Our part of the country is known as the eastern-forested zone and we have frogs, turtles, salamanders, a few snakes and no lizards.

There is one species of toad (American Toad) in our area, 3 types of tree frogs (grey treefrog, spring peeper and chorus frog), 3 types of forest/field frogs (leopard frog, wood frog, and pickerel frog) and 3 types of aquatic frogs (bullfrog, green frog and mink frog). It was noted that no deformed frogs were found during the study.

There are 6 types of snakes in our area with the main three being the garter snake, the ribbon snake and the black water snake.

Dr. Cook explained the differences between the various types of frogs and how the various species breed at different times of the year. A tool used to measure the number and activity of frogs is to go out at night and listen to their calling, which they do during mating season. Dr. Cook noted that this is getting more difficult with increased urbanization and increased night time road traffic.

Turtles on the Rideau
by Mike Rankin

Dr. Rankin noted that the two most common turtles in our area are the Midland Painted Turtle and the Snapping Turtle. He brought along live examples of each type of turtle, which he showed to the audience. He noted that we most often see turtles when they are basking, which they do to digest food. They ideally need to raise their body temperature to 65°F (18°C) in order to properly digest food, so they crawl out onto a log to bask in the sun, digest for a while, and then return to the water to hunt again.

The study has faced problems in trapping turtles. Initially lobster type traps, baited with sardines were used. It was note that this produced a selective catch, mostly adult males. Female turtles were not attracted to smelly fish and very few juvenile turtles were caught in the trap. One possible reason is that turtles don’t tend to like dead meat, they are not scavengers, they prefer live prey. A new idea is to use basking traps, to catch turtles when they come out to bask. This, in theory, should catch a diversity of age and sex.

The turtles, when caught, were marked and released. Marking involves filing a notch in the edge of the shell. The areas in which the notch is filed indicates month and year of marking. A new technique of using a small electronic tag, similar to that used with pets, will be tried in the future. Current studies indicate that the most common turtle on the Rideau, the Painted Turtle, is a homebody, staying within a restricted range, usually on the order of 100 feet (30 m) or less.

The Snapping Turtle spends most of its time in water, moving into shallow water areas to digest rather than getting out of the water to bask. They have little barbs under their chins which act as sensors to find prey in murky waters. Snapping turtles have an extremely powerful bite but they are shy of humans and given a chance will avoid human contact.

Dr Rankin showed examples of much rarer species found in the Rideau. These include the Musk Turtle, of which only one was seen in the study. It is a small turtle which likes to eat snails. It walks on the bottom of rivers or lakes rather than swimming. The Blanding Turtle has a chrome yellow throat. Only a few have been found in the Rideau, it is not their normal habitat. The Map Turtle has a brownish ridged back carapace with yellow lines. They like big rivers and big lakes. The males are half the size of the females. They make nests close to the waters edge. This makes these nests susceptible to damage by wave action, including boat wash.

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