过去7周内,渥太华河西部2公里之内发现5条死亡的大鲟鱼。

lindamy

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Egan: Is something killing the great sturgeon of the Ottawa River?

"I've had confirmation of five dead sturgeon found between the Lighthouse and the Point Beach in the past seven weeks."


Author of the article:
Kelly Egan
Publishing date:
Aug 29, 2020 • Last Updated 2 hours ago • 4 minute read

This Lake Sturgeon washed up dead on the Ottawa River at Constance Bay last weekend. It measured close to four feet long. It is one of several found on this stretch of river west of Ottawa and biologists are wondering what is causing the mortality.  For Kelly Egan story

This lake sturgeon washed up dead on the Ottawa River at Constance Bay last weekend. It measured close to four feet long. It is one of several found on this stretch of river west of Ottawa and biologists are wondering what is causing the mortality. PHOTO BY KELLY EGAN /Postmedia

On the weekend of Aug. 23, a large fish washed up dead on the sandy shores of Constance Bay, overturned on its thin white belly, strange little whiskers pointing to the sky.
It was a sturgeon — more properly a lake sturgeon — about four feet long and likely weighing in excess of 30 pounds. Neighbours, beach-walkers, began to chatter. Not only was it a rare sight, but it also wasn’t the first one this summer.

“I’ve had confirmation of five dead sturgeon found between the Lighthouse and the Point Beach in the past seven weeks,” Gerry Blyth later wrote, in describing a stretch of about two kilometres of the Ottawa River west of the city.

A resident of the shoreline for 31 years, he’d never seen a single dead sturgeon before. The question leapt to mind: Was something killing the most monstrous thing in the river, pre-historic fish that live for decades and can grow to six feet or even longer?

Well, no one is sure, and it is possible this is a strange clustering that has a perfectly sound explanation, like a natural die-off or mortality due to an angling misadventure.

Or not. The Ottawa, because of the scorching summer — July was the second hottest on record — is unusually warm right now and a quick call to a biologist reveals sturgeon are under stress if the water gets cooking.

So begins the detective work.

The City of Ottawa, it turns out, carefully tracks the temperature of the river at its two drinking-water intakes. (The precise reading actually affects the water treatment process.)
In July, the average temperature of the river at Britannia was 24.9 C, a full 1.5 degrees higher than the 10-year average of 23.4. August was higher as well, with average readings so far this month of 24.6 C, versus the historic average of 23.6 C.

And something else: In three of the past 12 years, the temperature of the river never rose above 25 C. Not for one day. This year, it has exceeded 25 C on 26 days, the highest number since at least 2009.

(The flip side of this is that the number of days that represent prime spawning temperature — an important trigger for egg laying/fertilizing — was vastly reduced. There were only eight days in 2020 when the temperature was between 11 and 15 C. Last year, the number was 34.)

OTTAWA - August 28, 2020 – Graph shows the Ottawa River temperature profile for the last five years, with 2020 shown as a black line.  Although 2020 is on the high side, we have observed similar trends in previous years.  The graph also indicates that our intake water is <1 °C for about five months per year, which is actually more challenging for the water treatment process due to chemistry and physical effects.  However, in most years, the river rises up to a comfortable swimming temperature, at least for a few months.

This graph shows the Ottawa River temperature profile for the last five years, with 2020 shown as a black line. PHOTO BY IAN DOUGLAS, ENGINEER, WATER QUALITY /City of Ottawa

The Ottawa Riverkeeper was keenly interested in all this.

Inhouse biologist Katy Alambo has canvassed some sturgeon experts and discovered that, indeed, the giant bottom-feeding fish are under stress when the water gets too warm, as warmer water contains less dissolved oxygen.

“Fish are very susceptible to rapid changes in temperatures,” she said Friday. “They can cause physiological stress to fish, lead to changes in the immune system and make them vulnerable to pathogens or viruses.”

She wondered, too, about periods of torrential rain this summer and whether the runoff was pumping in extra nutrients.

There is likely no cause for alarm. Neither the Ministry of Natural Resources and Forestry nor the Riverkeeper have had any reports about large fish die-offs on the Ottawa this summer, sturgeon or otherwise.

Blyth, meanwhile, said the discovery of the dead sturgeon sent him on an online dive into about possible causes. There are, in fact, a good number of scholarly articles about lake sturgeon in eastern North America, including in the Ottawa.

Among the findings? They like flowing watercourses and the damming of major rivers has had a detrimental effect on populations just about everywhere, including here. Not only that, adds Blyth, but the way some dams practise “peaking” — or alternating between still and rushing water — can also negatively affect the spawning period.

OTTAWA - August 28, 2020 –

25 °C. We have recorded this sustained high temperature effect in previous years – in 2018 (25 days >25 °C) and 2010-2012 (15-21 days >25 °C). In some years, the river never crests above 25 °C. Credit: Ian Douglas, Engineer, Water Quality. For: 0829 col egan fish" />The Ottawa River temperature was warmer this summer, although similar temperatures have been recorded in the past. City staff monitor river temperature at both water treatment plant intakes. PHOTO BY IAN DOUGLAS, ENGINEER, WATER QUALITY /City of Ottawa
There is a lots of lore about sturgeon on the Ottawa. Some of it is even true.

In March 1931, the Globe and Mail reported a specimen weighting 216 pounds was caught in the Ottawa near Montebello. In 1952, a fisherman near Davidson, Que., was in disbelief after a 35-pounder jumped right in his boat.

The Ottawa once had a thriving commercial fishery and, in 1898, more than 65,000 pounds were harvested. The Pembroke Observer, in the 1950s, carried a photo of sturgeon stacked on shore like cordwood: all to be used as fertilizer, which seems a horrible waste.

With their outer plates and spiky ridges, they are both distinct-looking and exceedingly long-lived, some lasting more than 100 years. Their life cycle is unusual, only becoming sexually mature after 15 to 18 years, while females only spawn every second or third year.

Should any more dead sturgeon show up, the Riverkeeper would like to know. Alambo asked that residents record the time and place, take photos and note anything unusual about the circumstances.

And be not afraid. Sturgeon, who would have thought, have no teeth.

To contact Kelly Egan, please call 613-291-6265 or email kegan@postmedia.com

Twitter.com/kellyegancolumn

 

Teddy

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GuardianAngel

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真没想到Ottawa river has these big fish
 

日新

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因为污染吗?
 

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我想看看自定义头衔到底能有多少字。继续加,看系统什么时候把这个字符串截断。呃,居然还有?那就继续吧。
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我爱健身

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真是孤陋寡闻 ottawa河里还有如此大物!
 

lindamy

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因为污染吗?
一楼文章里说,今年夏天,还没过完,超过25C天数是近11年中最多的。
 

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From where?

粉笔河核电站。渥太华河上游,开车 2小时。 1952年发生过一次迷你切尔诺贝利事件。 据说是核工业史上第一次严重核事故
当时清理出数千升的放射性毒水和其他受污染的反应器残骸等放射性废物,都埋在核电站附近的沙土里。
渥太华河如果有活了100年的鱼,那都是喝过辐射水的鱼
 
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