Sunday, 26 June 2016 09:56

Hanging Culverts… tightening the noose on fish habitat

Written by Michael Short
Rate this item
(0 votes)

There are thousands of kilometers of roads in Alberta. Both highways and small backcountry gravel or dirt roads pass over rivers and small streams. In many instances culverts are used to allow the water to continue to flow once a road is built crossing the stream or river.

Resource roads in Alberta pass over many rivers and streams

At first glance culverts appear to be the perfect solution to a river crossing. For the most part they are less expensive than bridge construction and have a relatively low maintenance cost. In some situations however, culverts are not maintained at all. Still culverts make an ideal alternative to bridge-building — especially in the case of temporary roads built by the oil and gas or forestry industries.

Yet not every culvert is created equal. Over time erosion on the down stream side of the culvert will create a drop off — and in some cases — one so severe it is impossible for fish to continue to swim up stream. This is a common situation for Arctic grayling that cuts the fish population off from traditional spawning grounds and can deny access to territory more suitable for population growth.

Such is the plight facing wild grayling stocks in the Swan River watershed. A small team of biologists from the Alberta Conservation Association started to look at the grayling populations in the Swan Hills area a few years ago.

Biologists survey grayling populations

The first component was to assess and catalogue stream crossings within the drainage system. The second component was to sample streams throughout the watershed to determine the relative abundance, distribution and population structure of the Swan River Arctic grayling population.

Stream crossing assessments revealed that 25% (737 kilometers) of the streams were fragmented due to blocked or hanging culverts. Habitat fragmentation was most common in smaller, headwater streams. ACA biologists inspected 218 crossings throughout the watershed, 195 existing stream crossings that were originally assessed in 2002. A total of 142 stream crossings were identified in fish bearing streams of which only 11% permitted fish passage. Current crossing data showed that there has been little to no change to the existing crossings first assessed in 2002.

Being separated from their traditional spawning grounds is having a dramatic impact on the fish population. Last year during a fish survey of 62 sites, biologists managed to catch a total of 431 grayling — but only six adult grayling — all the rest were juveniles.

Cataloging grayling length

ACA Biologist Brad Hurkett walks us through some of the obstacles being faced by the Arctic Grayling in this area.

Feature Podcast with Brad Hurkett

See first hand how culverts are impacting fish movement within the Swan Hills drainage area.


Of course this issue is not limited to just the Swan Hills area. For example, take the trout populations along the eastern foothills. Trout Unlimited, along with Husky Oil, recognized concerns with a river crossing in the upper reaches of Prairie Creek.

The need for a coordinated approach to repair, and even the removal, of a large number of culverts across the province is needed. There is indication the province and industry may be close to announcing a joint program — let’s hope so, as the day is fast approaching where the noose around grayling species health just might be tightened to the point of no return.

Photo Gallery

Read 8930 times