A gi­ant fish story

Lake stur­geon con­tinue to re­cover from be­ing a threat­ened species

Lethbridge Herald - - HOMETOWN NEWS | SOUTHERN ALBERTA - Tim Kali­nowski tkali­nowski@leth­bridge­herald.com

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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Pho­tos cour­tesy of Al­berta Fish­eries and Wildlife

Lake stur­geon pop­u­la­tions seem to be on the road to re­cov­ery in the South Saskatchewan River basin, but pro­tec­tions need to con­tinue, says se­nior fish­eries bi­ol­o­gist Shane Petry.

Lake Stur­geon re­main a prize catch for lo­cal an­glers in the Old­man River, and a spe­cial en­counter for those who catch these pre­his­toric-look­ing crea­tures on the end of their lines.

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