A giant fish story
Lake sturgeon continue to recover from being a threatened species
While lake sturgeon season has come and gone for anglers on the Oldman River as these large, ancient fish have now made their way back to their over-wintering water pools in the South Saskatchewan, Shane Petry, senior fisheries biologist with Alberta Environment and Parks, says there are encouraging signs of the species continuing recovery after being pushed to the brink over a decade ago.
“We have seen some increases in both the North and South Saskatchewan River basins since the year 2000 or so,” confirms Petry. “There has been some reproduction-driven increases in population. They were listed as threatened in 2007; before that one of the key things was we allowed harvest of lake sturgeon. But we have prevented harvest since about 2004 or 2005 down in the South Saskatchewan. That, of course, has a big effect on survival and ability to reproduce of mature fish.”
The benefits of increased survival rates among the mature fish cannot be overstated, says Petry.
“It is such a long-lived fish; they can live well over 100 years. So a lot of these fish were in these rivers before the dams were built, ranging great distances. Their lifespan is such they don’t sexually mature until they are older. A male might not mature and start to reproduce until that fish is 19 or 20 years old. And the female, you are talking maybe 23 or 24-plus years old until it is ready to reproduce.”
The larger and more mature the female of the species, the greater of the number of eggs she produces, says Petry. Sturgeon only reproduce every three to seven years even after reaching sexual maturity. An older female, however, will lay up to 500,000 eggs at once when she does reproduce.
“The data suggests they are likely reproducing in areas of the Oldman River, even around Lethbridge,” says Petry. “And they have been here longer than anything else for the most part. There are a few things about the fish which are unique. As mentioned, they outlive any other fish species. They don’t have bones and they don’t have scales. They have cartilage and what we call ‘scoots’; which are these bony plates along the lateral line on the side and across the top of the fish. It is an apex fish, and it consumes a lot of material from the bottom of the river. Whether that is decaying fish, worms, crayfish and all those sorts of things. Their mouth will actually protrude out like a vacuum hose to suck in food. And it has whiskers similar to a catfish which help it feel its way around.”
Petry says one thing which current fish have yet to recover from previous generations is their size. The sturgeon we have today aren’t exactly lightweights — tipping the scales at 100 pounds-plus. But this is quite small compared to past anecdotal evidence from previous decades where fish in the hundreds of pounds range were once caught in the South Saskatchewan. There may still be the odd giant out there, says Petry, and the evidence of it will likely come from the local angling community.
“We’ve had tremendous support from local anglers,” confirms Petry. “Many of these anglers are very passionate about lake sturgeon. We have sturgeon-angling specialists; it’s what they do. They love doing it, and they care about the species. They want this fish to be in our waters for many years to come. It is not uncommon to hook a large fish and have it breach the water by several feet. It’s a very challenging fish to angle, and really enjoyable. Angling is, of course allowed, with these fish in Alberta, but you are not allowed to harvest them. It’s strictly catch-andrelease.”
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