DFO to Install Counting Fence on Garnish River in NL

The Southern Gazette

Paul Herridge
Published on November 04, 2014

DFO plans to install counting fence on Garnish River

Scientists with the Department of Fisheries and Oceans hope to learn more about Atlantic salmon in Garnish River next year.

A counting fence will be installed next May, according to Carole Grant, head of DFO’s salmonid section in Newfoundland and Labrador.

Grant said the department has 16 monitoring facilities in the province where information on the upstream movement of adult salmon is gathered, 13 of which are DFO-funded.

Last year, it was determined that two locations — Northeast Brook in Trepassey and Salmon Brook on the Gander River — weren’t providing strong scientific data on the status of salmon stocks.

They have been dropped in favour of Garnish River and Northeast River in Placentia, Grant said, though a definitive decision has not been made on the latter.

“We felt we would be better served if we discontinued our monitoring activities on those two facilities and identified two new facilities throughout the province where we could get better information,” she said, explaining that counting fences allow DFO to monitor the health and abundance of Atlantic salmon stocks.

In some instances, DFO takes advantage of fishways that are already in place to help fish navigate natural obstructions and that can be manipulated to intercept the salmon as they move through the system.

Counting fences are built across with the same conduit used for electrical wiring.

“It’s not a barrier to fish because we’ll construct a trap with two gates, one that lets the fish in and another gate to let the fish out,” Grant said.

“If we want to retain the fish for purposes other than just counting, we can let the fish in through the one gate, hold them in the wooden trap, (take) whatever biological characteristics we want to do, and then release them by opening the other gate and letting them pass through.”

Grant said a number of environmental conditions need to be taken into consideration when installing a counting fence, including the location. Staying above the influence of salt water is important, but tributaries can have an effect if they are set up too far upstream.

“Ideally, you want to be as close to the mouth of the brook as possible to get a complete and accurate account of the fish that are moving into that system,” she said.

Grant said there are three main reasons why DFO settled on Garnish River for a salmon fence.

First, researchers would like to collect more information from the province’s south coast, where there currently aren’t a lot of counts.

Second, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has identified salmon as being threatened in the area.

And third, the potential for farmed salmon to escape from aquaculture sites entering Garnish River was a factor.

Grant said DFO plans to do an adult salmon count in 2015 with the intentions of completing a smolt count the following year.

There hasn’t been much research on Garnish River in the past, but scientists did carry out some electrofishing to catch juvenile salmon this past summer. Electrofishing involves zapping fish with an electrical current to temporarily stun them so they can be caught more easily. The fish are not permanently harmed during the process. About 200 samples were collected for DNA analysis over the winter.

 “Our geneticist will be able to determine whether or not they’re from a pure wild Atlantic salmon stock, whether they’re from a pure farmed stock or whether they’re a mixture,” Grant said.