by Erling Friis-Baastad
The Arctic grayling is one of the most elegant and sought-after fish of northern waters. Photographs of hefty grayling with their large dorsal fins spread wide are common in outdoors and travel magazines. So it’s surprising to learn that the photogenic and popular Arctic grayling was one of the species highlighted in Environment Yukon’s Status of Yukon Fisheries 2010 report as being overlooked by territorial research efforts, in favour of lake trout.
That actually began to change the year the report was released, says Environment Yukon fisheries biologist Lars Jessup. Arctic grayling, Thymallus arcticus, are hearty game fish of the Salmonidae family and can be found in cold waters throughout the territory. Despite the abundance of grayling in the Yukon, though, they can suffer from localized impacts, especially heavy angling pressure, says Jessup.
“One reason grayling haven’t been the focus is that they are shorter lived (than lake trout) and their reproductive potential is higher and they’re everywhere,” the biologist adds.
However, by the late 1990s, disturbing reports of diminished grayling fishing in certain areas created a sense of urgency. “So we decided to come up with a relatively quick and easy method to count grayling and try to be able to detect trends between years, to see if there were more one year than the next.”
As it turned out, donning a dry suit, climbing into the water and drifting over the fish is a quick, easy and effective way for biologists to tell how many fish there are in a particular reach. “We figured snorkel surveys were the best way to observe grayling in their own habitat efficiently with low impact; 2010 was the initial trial in the Lubbock River, and we continued in 2011.”
The Lubbock River connects Little Atlin Lake with Atlin Lake and, being grayling-rich and handy to Whitehorse, it long provided plenty of angling action, especially during spring spawning season. “The population there used to be very healthy. Everybody used to go and fish there first thing in spring and the population declined to the point where people were having a hard time catching them,” says Jessup.
Because of heavy impact on the Lubbock grayling during the late 1990s, regulations were introduced to reduce the harvest there. Lately, however, snorkeling scientists have clambered back onto the riverbank with some good news. “In the last two years we’ve been back to the Lubbock, we’ve seen quite a lot more grayling than we were actually expecting at first, so it seems like in the past 10 years, since the new regulations were put in place, the population is recovering a bit,” Jessup says.
As with the new burbot surveys (see Your Yukon #81- Lota lota: The Ugly Fish You Just Gotta Love) some simple arithmetic serves fisheries scientists as a powerful tool. Multiplication makes up for the fact that there are so many hiding places in a stream that scientists can’t hope to spot every fish.
It works like this: The researchers block off a section of stream with small-mesh nylon block nets above and below a targeted area. The small mesh prevents grayling from becoming entangled, while keeping them confined to one manageable area. Using good old-fashioned (but barbless) angling techniques, the scientists catch some grayling – usually about 10 – and then mark them with a brightly coloured version of the plastic T-bars one often finds holding together a newly purchased pair of socks. The tagged fish are gently returned to the blocked-off stretch of water.
The scientists then know that there are 10 tags in their blocked area; if, after multiple drifts over the section, they see an average of six tagged fish, they can deduce that their “snorkel-efficiency rate” is 60 per cent. They will extrapolate from that figure to determine the total number of grayling that are likely to be in the stretch, and what the average population density is per square metre.
Fisheries biologists are always eager to develop non-intrusive observation techniques, and the snorkel method is a major step toward that goal. After performing their counts and population extrapolation in a netted-off section, they target other areas of a river or stream that resemble the original reach in depth and visibility. Then they snorkel over these new unblocked sections, where they can assume that the snorkel success rate is also about 60 per cent. They perform the math and determine a population density, all without having to catch or tag a single additional fish. In time, researchers hope to get away from catching and tagging completely, says Jessup.
“It’s also really advantageous because, unlike a burbot survey or a lake trout survey, where you are capturing fish and bringing them up to the surface, when you’re snorkeling you get to see fish just behaving like fish, doing what they’d naturally be doing if you were not there,” he says.
“The other really cool thing we’ve discovered is, if you’re snorkeling and not thrashing around, not swimming – if you’re still and just drift over the grayling, they won’t even move.”
Unfortunately, not even this nifty testing method is universally effective. The tag-and-snorkel technique “works best in rivers and creeks that are shallow enough so you can see bottom,” says Jessup. Certainly, the creeks have to be deep enough for the scientists to float on them. “Otherwise you’d be crawling,” he says. That would disturb the fish, pebbles and any eggs that might have been laid during the spawning period.
At any rate, the new method is promising, and biologists hope to apply it to more creeks and rivers to monitor how the grayling are faring and make further, informed suggestions for managing them.
Meanwhile, this serious and demanding research is also “the most fun fisheries work I’ve ever done,” says Jessup.
This column is co-ordinated by the Yukon Research Centre with major financial support from Environment Yukon and Yukon College. The articles are archived at www.taiga.net/yourYukon.