Nathan Wilbur, ASF Director of New Brunswick Programs
Each winter, salmon anglers and conservation groups eagerly await the release of DFO’s adult salmon counts from the previous season. They tell us if populations are increasing or decreasing, and if they are sustainable relative to their minimum conservation egg requirements. For the Miramichi and Restigouche river systems in New Brunswick, the 2017 numbers are in. There’s some good news and bad, cause for optimism and caution, and like all things Atlantic salmon there’s some explaining to do.
The Miramichi River system, which drains about 25 per cent of central and eastern New Brunswick, has two main branches, the Southwest and Northwest. In order to assess adult returns on such a large system, DFO uses the ‘mark and recapture’ method. Trap nets are placed in the estuary of both branches, capturing a portion of returning adults entering from the sea. Once tagged, those salmon are released to head up river alongside fish that avoided the trap net.
Dungarvon counting facility that assists calculations for the SW Miramichi. Photo Nathan Wilbur/ASF
Along the way, tagged and untagged salmon are counted at assessment sites upriver, and by seining certain pools in the fall. In basic terms, by determining the proportion of tagged to untagged salmon, scientists estimate the percentage of fish caught in the trap nets and use that value to calculate an estimate of the total run.
Because 2017 was a low water year, fish spent more time milling around the estuary and were therefore caught more frequently in the trap nets – but this is accounted for in the final estimates. For all the details, check out the link to DFO’s full scientific assessment of the Miramichi at the end of this post.
Here are the highlights - In 2017 the total number of fish returning to the Miramichi system was estimated to be 14,600 large salmon and 13,300 grilse. These returns are down from 2016 and the trends for both salmon and grilse show a 25 per cent decrease over the last 12 years. This timeframe represents about two generations of Atlantic salmon.
Each branch has its own run of salmon, so there are yearly differences between the Northwest and Southwest Miramichi rivers. The Southwest branch had 10,700 large salmon and 8,100 grilse returns. There has been a 34 per cent decrease over the last 12 years for salmon and a 73 per cent decrease for grilse. The Northwest Miramichi had 3,800 large salmon and 5,000 grilse returns. While grilse have decreased 35 per cent, large salmon are showing an increasing trend on the Northwest and are up 20 per cent over the 12 year period, a good sign for egg deposition.
Overall, the Miramichi did not meet its minimum conservation egg requirement in 2017. After determining how many eggs entered the river in returning adults, and subtracting 2 per cent for removals by the aboriginal food, social, and ceremonial fishery, combined with mortality associated with live release angling, the Miramichi system reached 76 per cent of its minimum egg deposition requirement (83 per cent on the Southwest, 60 per cent on the Northwest). This minimum threshold is defined as 2.4 eggs per square metre of habitat. Below that level the population is at risk of not being able to sustain itself.
The beauty and serenity of casting on the Dungarvon River. Photo Nathan Wilbur/ASF
New counting methods are being tested on the Miramichi through the Collaboration for Atlantic Salmon Tomorrow. Researchers from the University of New Brunswick are using sonar cameras to count adult returns and it’s showing some early promise. There are advantages over the trap net method, like being able to count every fish and the ability to deploy cameras earlier and take them out later. For example, in 2017 a sonar camera on the Little Southwest Miramichi showed a good run of ‘salmon-sized fish’ (the camera can’t tell species – yet) moving upstream in late October and early November after the trap net had been removed.
The story of last season is brighter for the Restigouche. The river’s uniquely clear water allows for visual salmon counts, and combined with low water, assessment conditions were excellent last September when DFO carried out their snorkel surveys. The results will be published in February by DFO, but were released at meetings in Campbellton this week. The Restigouche system, excluding the Matapedia River tributary, had 2,461 grilse and 7,603 large salmonspawners. This count can be considered a minimum because it is the number of fish actually counted in the river prior to spawning. The count excludes salmon that were already removed in the aboriginal fisheries and mortality associated with live release.
Overall, the Restigouche system, excluding the Matapedia, attained 134 per cent of its minimum conservation requirement, which is defined as 1.68 eggs deposited per square metre of habitat. Note that this is lower than the conservation requirement for the Miramichi and other Gulf region rivers, so we are not comparing apples to apples. To provide some perspective, if we did use 2.4 eggs per square metre, the Restigouche would have achieved 94 per cent of its minimum conservation requirement.
DFO snorkel counts for each of the four main tributaries they assess, and the main stem of the Restigouche River, are as follows:
Numbers were much higher for the main stem because the count was conducted in September when many fish would have been staging in the bigger water prior to heading up tributaries to spawn in October. A good example is the Patapedia. It shows only 39 per cent of its conservation requirement achieved, but we know from previous years that counts conducted later in the season closer to spawning show higher numbers. In 2017, a mid-October count by Quebec’s Ministre des Forets, Faune et Parcs (MFFP) shows the Patapedia actually achieved 101 per cent.
Overall, the number of large salmon spawning in the Restigouche was a 20-year high. However, anglers may not have noticed because of poor fishing conditions for most of the season. Despite more fish in the system, New Brunswick Crown Reserve angling information for the Restigouche system shows catch per rod day decreased in 2017 by 11 per cent compared to the previous 5 year average.
Releasing a beautiful Atlantic salmon in the Kedgwick River where the egg deposition met the Conservation Limit. Photo Tommy Larocque
Assessments on the Quebec side of the Restigouche watershed conducted by MFFP show the Matapedia had an estimated 1830 large salmon returns (213 of these were harvested) and 440 grilse (358 harvested), resulting in egg deposition of 12.35 million eggs, or 119 per cent of its minimum egg requirement. Once again, the Quebec threshold is defined differently than those used in the New Brunswick portion of the Resitgouche and the Miramichi, but that’s another story.
Why was 2017 such a good year for the Restigouche system? A probable explanation is the ripple effect of 2011, which also had excellent adult returns. Considering that most Restigouche smolt go to sea when they are three years old, the large two sea-winter salmon returning in 2017 would have been eggs in the gravel in the fall of 2011, and there were a lot of them.
DFO Science reports on the Miramichi River, 2017: