Ten Threats: Saving an Ancient Fish

  • A juvenile lake sturgeon. (Photo courtesy of USFS, Rob Elliott)

Biologists have been concerned about a number of native species that
have been disappearing. One of them is the largest fish in the Great
Lakes. Over-fishing and gravel mining in riverbeds have wiped out 99-
percent of the population of lake sturgeon. Sturgeon used to be common
throughout the Great Lakes, but they’re a rare sight these days. Celeste
Headlee reports… biologists are trying to save some of the sturgeon’s
spawning grounds:

Transcript

We’ve been bringing you reports from the Great Lakes Radio
Consortium’s series ‘Ten Threats to the Great Lakes.’ Lester Graham is
our guide through the series. He says our next report is about an ancient
fish that’s been disappearing.


Biologists have been concerned about a number of native species that
have been disappearing. One of them is the largest fish in the Great
Lakes. Over-fishing and gravel mining in riverbeds have wiped out 99-
percent of the population of lake sturgeon. Sturgeon used to be common
throughout the Great Lakes, but they’re a rare sight these days. Celeste
Headlee reports… biologists are trying to save some of the sturgeon’s
spawning grounds:


(Sound of the lake)


Sturgeon are the largest fish in the Great Lakes. The grayish brown
creatures can grow up to seven feet long, and weigh more than 200
pounds. Sturgeon have been on Earth for 100 million years, and they’ve
remained essentially unchanged in all that time. Instead of scales, the
fish have an almost leathery skin with five rows of bony plates running
along their torpedo-shaped bodies.


Fish biologist Bruce Manny says sturgeon were once abundant in the
Great Lakes. Back in 1880, in one month’s time, fishermen pulled four
thousand of them from the Detroit River.


“They tore holes in their nets when they were fishing for other fish that
they cared about. So, when they found a sturgeon in their nets, they
would kill them, bring them to the shore, pile them up on shore, dry them
out and use them for fuel in the steamships. Burn them up.”


Most of the time, the creatures were caught and killed while fisherman
angled for more valuable fish. Scientists think over fishing has caused
sturgeon populations in all of the Great Lakes to dwindle to less than one
percent of their former number.


The state of Michigan closed the Detroit River to sturgeon-fishing years
ago. Bruce Manny says he decided to check on the sturgeon and see if
the fish population had started to recover.


Manny assembled a team of biologists from the U.S. Geological Survey.
He says he was surprised when his team caught only 86 fish over the
course of four years. Manny says he realized the sturgeon were in
serious trouble.


USGS scientists followed the tagged fish for two years, and their
patience was eventually rewarded. Manny found the first known
spawning site ever documented in Detroit River in modern times.


“We were excited all right. Eureka moment. I mean this is like a very,
very great coincidence that we were able to find these spawning ready
males, and they were able to find a female. When there are only 86 fish
caught in four years out here, there aren’t that many around. So, to find
someone to spawn with is a real challenge, I would say.”


The area where the sturgeon mated lies close to a sewer discharge pipe.
There are limp, brown grasses bordering grey, mucky water. Manny sent
divers down and discovered the fish had actually produced fertilized
eggs. Manny says this was a major step forward for his project.


Sturgeon are pretty picky about their nesting sites. They need a fast
moving current and several layers of rock where eggs rest safely. The
problem is a lot of the gravel has been mined out of the Detroit River for
use in construction.


Another problem is the sturgeons’ long life. Fish biologist Ron Bruch is
in Wisconsin. He oversees sturgeon populations in Wisconsin’s
Winnebago river system. He says female sturgeons live more than 100
years and they don’t spawn until they are at least 20 years old.


“Their life history works well for a long-lived species, but it doesn’t
work well for a species that’s exploited heavily. So, sturgeon can only
tolerate very low exploitation rates, and when that exploitation is high
the populations collapse.”


Wisconsin was the first state in the U.S. to create a sturgeon management
program more than 100 years ago, and the fish are more abundant there.


Biologists in Michigan monitored the nesting sites in the Detroit River
this spring. Eight species of fish used the beds, including popular sport
fish like yellow perch and walleye. Only two sturgeon came by the sites,
but they weren’t ready to spawn.


Ron Bruch says biologists will have to create a lot more spawning sites
like the ones in the Detroit River before the sturgeon population is firmly
reestablished in the Great Lakes.


“In and of itself, it’s not going to restore all of Lake Erie or all the Great
Lakes, but it’s a shining example of what can be done in many areas
around the Great Lakes to help produce Lake Sturgeon spawning habitat
and rehabilitate the Lake Sturgeon population.”


USGS biologists will go back to the nesting sites next spring. They say it may
take years for sturgeon to notice the small beds in the 32-mile river.


One important development, though, is a change of policy from the
Ontario Ministry of Natural Resources. Canadians used to allow
fisherman to take one sturgeon a day out of the river. Now, it’s illegal to
possess one of the endangered fish on both sides of the channel.


For the GLRC, I’m Celeste Headlee.

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