How did the fish cross the road?

As silly as it sounds, this is a very important question that can have a large impact on aquatic ecosystems. Aquatic connectivity is the distribution and movement of water across a landscape which can influence the health of fish populations and, ultimately, aquatic ecosystems. If not built properly, the roads and bridges we use to explore our parks can block movements of fish and other aquatic organisms that live in streams and rivers. Failing bridges and culverts can also generate tremendous amounts of harmful sediment through erosion and hydrocarbons from storm-water run-off. It is up to Parks Canada to ensure bridges and culverts are properly built and that infrastructure does not interrupt the aquatic landscape.

Some of the barriers infrastructure can create are:
  • Branches and rocks that block culverts and stop aquatic life from reaching all of their habitat.
  • Most fish like short sprints, not marathons. Long stretches of fast moving water with no resting place can tire some aquatic life, preventing them from moving upstream.
  • Fast water forced through a narrow culvert spins like a washing machine, making them impassible at key times of year.
  • Some fish can’t jump. Hanging culverts can create impassable waterfalls and keep fish from reaching their destinations and resources.
  • Fish and most aquatic life must have enough water. Dry periods and wide culverts can create thin layers of water too shallow for fish to swim through.

Do fish need to cross the road?

In other words, do fish really need to access all areas of their habitat? Are they able to adapt to the newly formed aquatic landscapes after infrastructure has been put in place? Fish need to move for a number of reasons:

To find food
To find spawning grounds
To find rearing areas
To find overwintering areas

All life is interconnected. Restricted or improper aquatic movement disrupts lifecycles and ecosystems and can make it impossible for fish populations to survive. This can result in lower numbers of fish, fewer species and less genetic diversity.

For these reasons maintaining aquatic connectivity is required by the Federal Fisheries Act, as well as the Canada National Parks Act and in many cases also the Species at Risk Act of Canada.


How is Parks Canada helping?

Parks Canada continues to evaluate existing infrastructure to ensure aquatic connectivity and new projects are built with ecological integrity as a top priority. Parks Canada is undertaking initiatives to ensure we better manage these connections.