Salmon decrease in Mackenzie supports local hunch

Salmon decrease in Mackenzie supports local hunch
Karen Dunmall prepares a Mackenzie salmon sample for DNA analysis back at the lab.Photo courtesy of Karen Dunmal.

A significant drop in the amount of salmon caught in the Mackenzie River system in 2012 helps confirm local knowledge that salmon populations run in five to seven-year cycles in the NWT.

PhD researcher Karen Dunmall of the University of Manitoba is in her second year of studying the genetics and population structures of Mackenzie salmon, which are becoming increasingly predominant throughout the river system, including as far south as Fort Liard and Fort Smith.

Though the salmon collections, done through the help of local fishermen, returned 226 fish in 2011, only 22 salmon were turned in for reward in 2012, supporting the local theory that there is a cyclical pattern to salmon in the Mackenzie.

“One of the big questions I got in 2011 was, ‘Did you get a lot of salmon because a lot more people were looking for them and handing them in, or did you get a lot of salmon because there were more salmon?’ And I didn’t know how to answer that until this year when we had the same amount or more people fishing and handing salmon in,” Dunmall told The Journal.

“People who were catching four or five salmon a day in 2011 didn’t catch any in a few instances or caught one or two in the whole season this year. They were the same nets, same location – basically everything was the same except the fish didn’t show up.”

Dunmall said that’s what people up and down the river had told her, that the chum salmon show up in a cycle.

“The cycle length seems to change depending on who I talk to and where they are on the river,” she said. “The closer to the mouth, it seems like it’s a shorter cycle; and then further up river in Fort Smith it seems like it’s a really long cycle. But definitely that’s what people said: ‘You’re not going to see a year like this for a while,’ referring to 2011. So it was something to keep my eye open for in 2012, and then when it actually happened, it was really interesting.”

A fisherman holds a pink salmon caught on Peel near Fort McPherson. (Photo courtesy of Karen Dunmall)

A fisherman holds a pink salmon caught on Peel near Fort McPherson. (Photo courtesy of Karen Dunmall)

Pink salmon, too, show up in two-year cycles. In 2011, only three of the 226 salmon caught were pink, whereas last year, half of the catch was pink salmon.

The majority of salmon caught in 2012 came from the Mackenzie Delta region, as pink salmon only migrate as far as Tsiigehtchic. The furthest upstream that a chum was caught last year was in Wrigley and one in Fort Liard.

The chum salmon that are coming back to the Mackenzie River are between three and five years old, Dunmall said. Because of that, it makes sense to see a pattern in an established population of chum salmon in the river system.
Dunmall said the observation, while helpful, opens up many more questions.

“It provides evidence for a population from the Mackenzie that returns every three to five years, except that the cycle length that people are telling me is longer than that, so that’s the part that I don’t know yet, is why would it be seven years or longer for people in Fort Smith, and why is it shorter for people closer to the mouth? Especially since salmon aren’t coming back as seven year-olds.”

She said there may be more than one population cycling at once, or salmon coming in that aren’t from the Mackenzie spawn, adding more strays to some years than others.

She hopes to figure some of that out in the next portion of her research, which looks at the genetics of the salmon samples, to see if there is more than one population of salmon in the Mackenzie and where they might be coming from.

Dunmall will also be comparing salmon caught in the Mackenzie to ones caught elsewhere to see if there are stray salmon coming in. She is heading to Anchorage, Alaska at the end of the month to start collaborating with researchers there to see if their salmon match.

She said population data on salmon in the Mackenzie could help contribute to addressing larger questions of if or how Arctic salmon are being affected by climate or ecosystem changes, and how an increase in salmon could impact other native fish species and the river itself.

“People were curious to know if salmon are increasing in the Mackenzie River and the potential for interaction between salmon and other species is also increasing. So are they competing for habitat, are they introducing diseases or pathogens from outside the system, all the dolly varden (trout) benefiting because they eat salmon eggs,…are there more nutrients in the river, because salmon come in and bring all these nutrients from the ocean and then die and leave it there?”

As of right now, she doesn’t have those answers, but she’s hoping the federal department of Fisheries and Oceans will allow her continue to research over the next three years.

“It’s a big question: is the ecosystem changing and is that why salmon are showing up in bigger numbers? To start addressing that first is to get a handle on the distribution and abundance year to year of salmon and then where they’re coming from.”

To get updates on Dunmall’s salmon study, visit arcticsalmon.ca or Arctic Salmon on Facebook.

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