Clear and Present Danger


Aug 28, 2019
A satellite view of Miramichi Lake shows the outlet, called Lake Brook, which connects to the Southwest Miramichi River. Google Earth
On August 22nd, 2019, following reports that a smallmouth bass was angled and released near the mouth of McKiel Brook in the Southwest Miramichi River, Dr. Allen Curry and a team from the Canadian Rivers Institute at the University of New Brunswick donned masks, snorkels, and fins and went looking underwater.

Eventually a photograph was taken showing a single smallmouth bass facing upstream; one image and one fish with the potential to devastate an ecosystem and the identity of an entire region.

The confirmation of a smallmouth bass in the Miramichi River is not a surprise, it’s a preventable tragedy a decade in the making.
Smallmouth bass originated in the Ohio River valley but have been widely introduced in lakes and rivers throughout North America. Illustration U.S.F.W.S.

A strange catch

In the summer of 2008, an angler in Miramichi Lake caught something unexpected – a smallmouth bass. A call was made to enforcement officers with the Province of New Brunswick’s Department of Natural Resources and an immediate response was triggered. Staff from Fisheries and Oceans Canada (DFO), which is the department constitutionally responsible for aquatic invasive species, and volunteers from the Miramichi Watershed Management Committee also became involved.
This image from October 2008 shows crews electrofishing in Miramichi Lake soon after smallmouth bass were confirmed. Courtesy N.B. Department of Energy and Resource Development
Gill nets were hung in likely bass hot spots, and in October a barrier was erected at the outlet of the lake which forms a 5.3 kilometer (3.3 mile) long watercourse that connects directly with the Southwest Miramichi. The presence of bass in Miramichi Lake was quickly confirmed and a provincial investigation determined they were illegally introduced, although no charges were laid.

The 2008 discovery marked the first-time smallmouth bass had been recorded in the Miramichi watershed, presenting a new, grave threat to native species and fisheries throughout the river valley.

DFO’s response

The following spring, DFO resumed efforts to contain smallmouth bass in the lake and study the extent and size of the illegally introduced population. The seasonal barrier, which is generally in place from May to October, was reinstalled and sampling confirmed smallmouth bass had successfully spawned that spring in the lake.

Nine years earlier, in 2001, chain pickerel were swiftly and effectively eradicated from another lake in the Southwest Miramichi watershed using rotenone. The treatment was carried out by the province and sanctioned by DFO and Environment Canada.

However, in the case of Miramichi Lake, citing "regulatory constraints", DFO-opted for a program to physically capture all smallmouth bass and contain their spread, even though this approach has not worked anywhere else.
The seasonal barrier at the outlet of Miramichi Lake has been operated between May and October since 2008. To accommodate migrating river herring, technicians regularly scoop thousands of small fish over the netting. Photo Neville Crabbe/ASF
In July 2017, DFO technicians removed the 6,000th smallmouth bass from Miramichi Lake, one of the young-of-the-year in this ziplock bag. Photo Neville Crabbe/ASF

In 2010, fyke nets and gill nets were deployed and a systematic electro-fishing effort by boat and backpack began. In that year 2,584 smallmouth bass were removed, followed by 523 in 2011 and 46 in 2012. Although the population was knocked back, the program failed to meet DFO’s own goal of no young-of-the-year smallmouth bass detected for three consecutive years. In fact, each year since 2008, smallmouth bass of all life-stages have been detected in the lake.

A looming threat

Smallmouth bass is not native to Atlantic Canada, although introductions in the region began as early as 1869. In a 2009 risk assessment looking at the threat posed by smallmouth to the Miramichi River ecosystem, DFO noted they existed already in 34 rivers and 69 lakes in New Brunswick, the result of widespread introductions and movement through interconnected waterways.

For example, in the Magaguadavic River in southwestern New Brunswick, which once supported healthy returns of wild Atlantic salmon, ASF researchers found smallmouth bass spread from a single headwater lake throughout the watershed, competing for habitat and consuming salmon and trout along the way.
ASF Vice President of Research Jonathan Carr holds a salmon parr found inside the mouth of a smallmouth bass caught in the Magaguadavic River in 2009. Photo Tom Moffatt/ASF
Smallmouth bass are voracious. As DFO writes in their 2009 risk assessment, “when [they] are introduced to a water body, they prey heavily on other fish, can outcompete other fish species, and can become a dominant component of the food web.” In the Miramichi River system, DFO concluded they would likely spread far and wide and result in a “measurable decrease in abundance of native populations.”

Beyond harmful changes to the ecosystem, the establishment of smallmouth bass in the Miramichi would fundamentally change the character of the river, as it has in the Nashwaak, Hammond, and St. Croix. Indigenous and recreational fisheries would be permanently and negatively altered.
A graph prepared by Canada’s Auditor General shows that dealing with the introduction of aquatic invasive species immediately prevents their establishment in the environment and saves potentially tens of millions of dollars in management costs. Office of the Auditor General

Better Tools

In 2015 the Government of Canada enacted Aquatic Invasive Species Regulations under the Fisheries Act. These new regulations gave the Minister of Fisheries and Oceans the authority to permit the deposit of deleterious substances in Canadian waters for the purpose of eradicating invasive species.

In large part, it meant the long-standing, safe, and environmentally responsible use of rotenone (pronounced: wrote-in-own) was enshrined in law and treatments could continue throughout the country. 

Health Canada, through the Pest Management Regulatory Agency, has evaluated the safety and efficacy of rotenone and has registered products for use in aquatic environments. 

Rotenone – what is it?

Rotenone is a naturally occurring organic compound found in the roots of several plants, notably the bean family. It is present throughout the world and has traditionally been used by Indigenous people to harvest fish by crushing the roots or stocks of plants where rotenone is present and sweeping them through water.
Rotenone is a naturally occurring organic compound widely used in fisheries management. It is extremely effective on target species like smallmouth bass but is safe for humans, birds, and mammals when used properly. Wikipedia
According to the American Fisheries Society, which has published guides for the public on safe and responsible use of rotenone, it was first used as a fisheries management tool in the United States in 1947. Since then, it has become the most common tool for eradicating aquatic invasive species worldwide.

Rotenone is particularly safe and effective because it is highly toxic to gill breathing organisms, inhibiting their ability to use oxygen, while waterfowl, birds, mammals, and amphibians are generally not affected when lakes and rivers are treated.

Rotenone breaks down rapidly in the environment, heavily influenced by water temperature and sunlight. Although it is generally safe for humans to resume recreational uses of waterways immediately after treatment by rotenone, guidelines on product labels advise a 72-hour interval after treatment before angling, swimming, or boating. 

Success stories

Rotenone has been used to maintain healthy, diverse aquatic ecosystems throughout the world. It is effective in small ponds and large reservoirs like Lake Davis in Northern California which has a surface area of nearly 1,200 hectares.

In British Columbia, the provincial ministry of environment began a campaign in 2004 to safeguard steelhead, Pacific salmon species, and other native fish in the Thompson River from smallmouth bass and yellow perch which were illegally introduced and discovered in 13 small lakes within the watershed.
An applicator boat distributes a diluted rotenone solution in Windy Lake near Kelowna, B.C in this September 2017 photo. The government of British Columbia aggressively targets illegal introductions of aquatic invasive fish to safeguard native species. Photo Neville Crabbe/ASF
In September 2017, representatives of the Atlantic Salmon Federation, the province of New Brunswick, and Fisheries and Oceans Canada travelled to the interior of British Columbia to observe the treatment of Windy Lake. Coupled with a public awareness campaign to prevent new introductions, B.C’s rotenone eradication program has successfully prevented smallmouth bass and yellow perch from entering the Thompson River.

In Norway, the Atlantic salmon parasite Gyrodactylus salaris was introduced through transfers of salmon and trout from Sweden in the 1970’s and quickly became the most acute threat to wild salmon in the country, capable of extirpating entire river populations in four to six years.

The parasite eventually spread to 50 rivers and Norwegian authorities began a campaign to eradicate the parasite by denying it a host. Live gene banks and milt banks were established and entire rivers were treated with rotenone, removing all wild salmon. Among the largest was the Rauma River, which was treated in 2014 and subsequently declared parasite free.

To date, of the 50 rivers infected with Gyrodactylus salaris, 32 have been declared parasite free and salmon have been reintroduced, 11 others have been treated and are awaiting final analysis while seven rivers remain infected. Through the use of rotenone, the eradication of Gyrodactylus salaris in Norway is possible.
The parasite Gyrodactylus salaris was introduced to Norway in the 1970s with devastating consequences for wild Atlantic salmon. Norwegian authorities are on the brink of eradicating the parasite through the use of rotenone. Photo Jannicke Wiik Nielsen Veterinaerinstituttet

The plan for Miramichi Lake

After the passage of Canada's Aquatic Invasive Species Regulations, in 2016 First Nations and conservation NGOs came together to form the Working Group on Smallmouth Bass Eradication in Miramichi Lake. Founding members include the Atlantic Salmon Federation, Miramichi Salmon Association, Miramichi Watershed Management Committee, New Brunswick Salmon Council, New Brunswick Wildlife Federation, and the North Shore Micmac District Council. In 2018, the Maliseet Nation Conservation Council joined the Working Group.

Our first task was to commission an expert report to assess options, feasibility, and technical requirements for eradicating smallmouth bass from Miramichi Lake. Dr. Michael van den Heuvel from the Canadian Rivers Institute and Brian Finlayson, a California based expert on aquatic invasive species eradication, were hired. In July 2017 a final report was delivered.

The authors concluded that eradication of smallmouth bass in Miramichi Lake using rotenone is the best option. It is technically feasible with a very high likelihood of success. They evaluated alternatives, including dewatering the entire lake, and found that none would work and could result in serious long-term damage to the ecosystem.
Brian Finalyson, right, surveys the barrier at the outlet of Miramichi Lake in this July 2017 photo. Finalyson is a renowned expert on aquatic invasive species and was hired to produce a report on the eradication of smallmouth bass from Miramichi Lake. Photo Neville Crabbe
The expert report was presented to DFO at a July 2017 meeting in Moncton. Finally, in July 2018, through a letter from then Fisheries Minister Dominic LeBlanc, the Working Group was informed that “the department’s preferred approach is to continue to use physical control techniques,” and that DFO would not take on the eradication project themselves, instead choosing to stand back and regulate.

In response, the North Shore Micmac District Council stepped up and volunteered to be the proponent with support from members of the Working Group. An official application to eradicate was submitted to DFO on April 9, 2019, about 4 months before the eventual discovery of smallmouth bass in the Southwest Miramichi River.

The Working Group on Smallmouth Bass Eradication remains determined to definitively deal with the situation. A provincial environmental assessment has been ordered and dialogue continues with officials in Fredericton and DFO’s Gulf Fisheries Centre in Moncton.

Responding to the spread of smallmouth bass
A photograph from UNB’s Dr. Allen Curry captured the first known occurrence of smallmouth bass in the Miramichi River on August 22nd 2019. Photo Dr. Allen Curry
The August 22nd photograph taken by UNB’s Dr. Allen Curry at the mouth of McKiel Brook, approximately eight kilometres downstream of Miramichi Lake, is confirmation of what experts on aquatic invasive species have said since day one: containment and removal will not work and as long as smallmouth bass remain in Miramichi Lake, their spread is inevitable.
DFO, the province of New Brunswick, and all members of the Working Group have mobilized to gauge the extent and distribution of smallmouth bass in the Southwest Miramichi. This effort will include seining with nets, environmental DNA sampling, and electrofishing.

Once the magnitude of the invasion can be determined, including removing the photographed fish, a plan will be devised. According to the International Union for the Conservation of Nature, next to habitat loss, invasive species pose the greatest threat to biodiversity worldwide.

It will take the entire salmon community working together to preserve the integrity of the Miramichi for future generations. An entire ecosystem hangs in the balance.

Our elected representatives and officials at Fisheries and Oceans Canada must step forward and show decisive leadership before it's too late. Canada possesses the regulatory tools and resources to do the right thing.
Merlin Palmer: Merlin Palmer poles a canoe in the Southwest Miramichi in September 2015. Wild Atlantic salmon are at the centre of a vibrant river culture in the Miramichi River valley. The recreational fishery alone employs more than 600 people every year. Photo Nathan Wilbur

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