Largest ever Cowichan Lake fish survey nets positive results

The largest-scale fish survey on Cowichan Lake to date has yielded some interesting results.

  • Mon Jul 18th, 2011 11:00am
  • News

The largest-scale fish survey on Cowichan Lake to date has yielded some interesting results.

One of the more interesting results is a potential upswing in coho populations, with survey results estimating two million coho fingerlings in the lake.

“That was a really good sign, because coho numbers were decreasing. Now we’re seeing a rebound,” Cowichan Lake and River Stewardship Society member Gerald Thom said.

The fish survey was a partnership between volunteers at the society and the Department of Fisheries and Oceans.

The survey effort started last year, and included the classification of various shoreline types, and a check for disturbance of habitat, among other environmental forces that affect fish populations.

This year’s work helped back up last year’s observations, with volunteers taking care of fish surveys from June 29 to July 7.

“It’s part of an ongoing project to survey the lake to determine the next priority locations for protection,” Thom said.

Three methods of sampling to determine fish populations were employed, including;

• Seine nets were used to capture everything within a specific area.

• Snorkel survey, wherein three people went in, surveying areas 10 feet in, 20 feet in, and 30 feet into Cowichan Lake.

Fish counts and fish types were noted.

• Baited minnow traps were deployed over a 24 hour period.

The top-counted species of fish, in decreasing order of prevalence, were;

1) Coho salmon

2) Sticklebacks

3) Sculpins

4) Cutthroat trout

5) Rainbow trout

6) Kokanee

7) Chinook salmon

It wasn’t only the species of fish and the number of said fish that was interesting to the surveyors.

The location that fish were found will help determine priority areas for future protection.

“95 per cent of the fish were found within the first 10 feet of the shoreline,” Thom said.

Overhanging trees provide shelter and insect drop, Thom clarified.

Areas with aquatic vegetation have also proven themselves valuable in fostering high fish populations.

“I wouldn’t imagine that in water two feet deep and less, that’s where the fish are!” Thom said.

The location of these fish brings further credence to the importance of riparian zones – shoreline areas protected by law, and meant to stay in their native state.

A couple of key areas with high numbers of fish swimming about shallow waters with overhanging trees include the Marble Bay and Bear Lake areas.

This large-scale survey will be combined with other such fisheries studies to be analyzed and used by the Department of Fisheries and Oceans while setting future conservation goals.