When Invasive Species Threaten the Future of Wild Atlantic Salmon Rivers

Do we ever have good news on invasive species affecting wild Atlantic salmon?


In Norway, a parasite named Gyrodactylus has greatly impacted a number of Atlantic salmon rivers. It is native to Sweden, Finland and parts of Russia, and was introduced through "human vectors", meaning anglers, kayakers, and other boaters. It doesn't have a truly major impact in its rivers of origin, but in Norway it was devastating. Fortunately many of the very top Norwegian salmon rivers were never contaminated, but it did impact dozens of others.

This week eight rivers half way up this very north-south country were declared free of the parasite. The Vefsna, Drevjo, Halsanelva, Hestdalselva, Ranelva, Leirelva, Dagsvikelva and Nylandselva are now completely free of the parasite.

Fosjordi beat on the Vefsna River. This and other nearby rivers are now free of the Gyrodactylus parasite and will be open to anglers again next season.

How did the Norwegians solve this problem that plagued these rivers for more than a decade? They used Rotenone to kill it, along with the other fauna of the river, and encouraging the re-establishment of a natural, balanced ecosystem of the native flora and fauna.

The Norwegians now are very careful about treating angling and boating equipment to avoid any repeat, but it was the Rotenone that allowed restoration and elimination of the invasive.

The good news is continuing. There is a rumour that another famous Norwegian river, the Laerdal, will soon be declared Gyrodactylus free thanks to Rotenone treatments.

When Atlantic salmon in particular, and a natural ecosystem in general are impacted by invasive species, the invasives can send all into a tailspin from which they may never recover. In this case the rotenone has save these rivers for the future of all, and returned a balance in these waters, perhaps for centuries into the future.


Charles Cusson, ASF Director of Quebec Programs, reports:

The season ended on Saturday September 30.  Mother Nature helped anglers out for the last few days by providing some much-needed rain.  Rivers like the Matapedia saw its level come up at least one foot. All we can do now is hope a little more rain comes to salmon country to help the fish still in the estuaries to have an easier time migrating to their spawning beds.

With tough angling conditions for most of the season, the number of fish returning to their rivers was down and in some instances. In others, returns were somewhat better than the previous years going back to 2013. 

Full official data on the rivers should be available in late January or early February, 2018.

On the final day of the season, Sept. 30, 2017, ASF's Charles Cusson releases a healthy wild salmon at Hell's Gate Pool on the Matapedia River.  Photo Daniel Bélanger

Final day of salmon season - Sept. 30 at Milnikek Pool on the Matapedia River, with fall colours intensifying. Photo Charles Cusson/ASF

With a splash it is off! ASF's Bill Taylor releases a 20 lb. male salmon on the Cascapedia Sept. 25, 2017. Photo ASF

Autumn colours reflect in Hell's Gate Pool on the Matapedia River, Sept. 30, 2017.  Photo Charles Cusson

New Brunswick

The first two weeks of October are a magical time on New Brunswick rivers, with fall colours. The tinge of brightness flares into a blaze along the river. River temperatures dip, and together with their seasonal urgency the Atlantic salmon show more power and movement. And this is just before the leaves drop in the water, fouling the salmon line!

Cains River, tributary of the Southwest Miramichi, on a morning in early October. Photo Nathan Wilbur/ASF

Brock Curtis of Curtis Miramichi Outfitters in Blackville says:

We have a lot of anglers here on the Miramichi enjoying good fishing and the beautiful fall colors. Last weeks rain seemed to wake the river up and quite a few anglers are catching salmon. One report today was of a 40 lb salmon hooked and released. The river is dropping off again but angling seems to remain good. We just can't seem to keep up with fly patterns in the 10's and 12's sizes. Normally this time of year we are into fall rains and larger sizes are the norm. The long range forecast is showing some rain so we should continue to see good fishing through to the 15th.

Early October view on a foggy October morning a year ago at Wilson's on the Southwest Miramichi. Photo Nathan Wilbur/ASF


Trapnet totals on the Miramichi were available:

The Millerton Trapnet on the Southwest Miramichi has counted 612 grilse and 327 large salmon to Sept. 30, 2017, vs. 940 grilse and 666 large salmon  to the same date in 2016. Even the terrible year of 2014 had more grilse, with 631, along with 426 large salmon

On the Northwest Miramichi the Cassilis Trapnet has counted 563 grilse and 341 large salmon to Sept. 30, vs 428 grilse and 433 large salmon to the same date in 2016.

For the counting fences - the Dungarvon Fence had 4 grilse and no large salmon through the week. Thus their numbers to Oct. 1 were 98 grilse and 122 large salmon. Last year to the same date, they had 153 grilse and 118 large salmon.

For the Northwest Miramichi Barrier, there were 134 grilse and 120 large salmon to Oct. 1, vs 235 grilse and 81 large salmon in 2016. Thus for the week to Oct. 1, there were only three grilse.

An October salmon in 2015 being released near Wilson's on the Southwest Miramichi.  Photo Nathan Wilbur/ASF

Newfoundland and Labrador

Just prior to sending out the ASF RIVERNOTES, the Oct. 1 numbers were posted, on Thursday.

Don Ivany, ASF Director of Programs for Newfoundland and Labrador notes:

Fishing has been slow on the Lower Humber this past week mainly because water levels are high and the few fish that are in the system (mainly dark) are spread out more and difficult to find. So a slow end to the fishery which is due to close on this Saturday (Oct 7).

Fred Parsons reports slow fishing on the Exploits River.  They stopped counting fish this past Sunday at Bishops and did not get a fish through the fishway in the previous four days before closing the fishway.

On the Gander, Tolson Parsons reports:

Water levels are now good, but very few salmon. Overall, a very poor season, as we all know.

In Labrador, only English River had increased numbers in the week leading up to Sept. 24. There was no change in numbers to Oct. 1.

Pinware River in Labrador in a previous summer. Photo Nathan Wilbur/ASF

Nova Scotia


Alex Breckenridge, "the Tying Scotsman" notes:

With the last high water around the weekend, fish are once again throughout the system. Prior to that fish were showing but for most anglers no takers. A good weekend reported by customers at the shop.

Greg Lovely says of the Northeast Margaree on Monday:

We had great water for a few days after the last good rain and there were fish being caught up and down the river. The water levels have now dropped and so has the catching. A few lucky anglers are still catching salmon daily, but they are working pretty hard to get the salmon to take. The mornings are now quite cool which is good for the fish. I have seen "practice redds" in some of the pools.

and added on Tuesday:

I poked around the river today and saw quite a few fish in five or six of the "main" holding pools. I managed to convince a nice wild male salmon to take my fly.

Northumberland Strait Rivers

Lewis Hinks, ASF Director of Programs for Nova Scotia and Prince Edward Island says:

The water is very low on all the Northumberland Strait rivers.  A few fish are poking into the lower tidal pools but everyone, including the salmon, are waiting on a substantial rain. The rain we had last week did raise the rivers, but the ground is so dry that it ran off just as quickly.


Penobscot - The web editor asked Jason Valliere, Scientist with the Maine Marine Resources, for a breakdown of fish allowed to proceed beyond the Milford Fishlift, and those collected for breeding at the Craig Brook Center in East Orland, ME.

313 were allowed to proceed upstream

517 were removed to go to the Craig Brook Hatchery

2 mortalities in the Milford Fishlift.

The US system relies on a heavy dose of hatchery augmentation. Whether that focus should be revisited in the future is a matter for writers perhaps a decade or two from now.

French Island, Penobscot River.