Ten Threats: The American Eel

  • Researchers measuring an American Eel. (Courtesy of United States Department of Agriculture)

Pollution and invasive species are killing off or crowding out native plants and animals,
but for some species, it’s not just one problem, but many problems that are hurting them.
Few species illustrate the dangers of the multiple threats to the Great Lakes as the American
eel. Only fifty years ago, the snake-like fish accounted for half of the biomass in Lake
Ontario. Today, it has all but disappeared. David Sommerstein has that story:

Transcript

In our next report in the series Ten Threats to the Great Lakes we hear about native
species that are in trouble. Our guide in the series is Lester Graham. He says some fish
and organisms are disappearing.


Pollution and invasive species are killing off or crowding out native plants and animals,
but for some species, it’s not just one problem, but many problems that are hurting them.
Few species illustrate the dangers of the multiple threats to the Great Lakes as the American
eel. Only fifty years ago, the snake-like fish accounted for half of the biomass in Lake
Ontario. Today, it has all but disappeared. David Sommerstein has that story:


Before you say, who cares about a slimy critter like an eel, eels are amazing. They spawn
in the Sargasso Sea, the Bermuda Triangle, but no one’s ever caught them in the act.


After they’re born, they’re like tiny glassy leaves. They float thousands of miles north
and west on ocean currents. Then, they wiggle up the St. Lawrence River and into the
Great Lakes. They live up to 20 years in fresh water before they start the long journey to
the Sargasso to spawn.


The problem is their offspring are not coming back. People are worried about the eel, and
those who relied on it for a living feel like they’re disappearing too.


(Sound of waves)


Just ask fisherman John Rorabeck. He grew up here by the lighthouse on Point Traverse,
a peninsula that juts out into northeastern Lake Ontario.


Rorabeck’s been fishing these waters for more than 30 years. Eels were his prime catch.
He points past the lighthouse.


“I remember when I started fishing there were nights on that south shore, the most fish
that would be eels at certain times and there was literally tons of them on that south
shore. Now, you could go back there and you’ll find nothing.”


Rorabeck stopped fishing eels several years ago because it just wasn’t worth it. Now he
dedicates his fishing time to science. He catches specimens for leading eel expert John
Casselman, who examines them in his lab.


“It is truly a crisis. A crisis of concern.”


Casselman’s a scientist at Queens University in Kingston, Ontario. In 1980, at a point on
the St. Lawrence River in mid-summer, he counted more than 25,000 eels a day. Now
there are as few as 20 a day.


Casselman ticks off a list of causes. It sounds like a who’s who of environmental threats
to the Great Lakes – over fishing, dammed up rivers, erosion, pollution, invasive species,
climate change. If scientists could sift out how all the factors relate, they could take a big
step in better understanding the Great Lakes delicate ecosystem.


The problem is, Casselman says, there’s no time to wait. In 2003, eel experts from 18
countries made an unusual statement. In what they called the Quebec Declaration of
Concern, they urged more action, not more science.


“I’m a research scientist, and of course I love data. At this point, you don’t want me.
Don’t ask me to explain what’s going on here because by the time I get it figured out, it
may be too late.”


People are starting to do something about it, Casselman says. Several U.S. agencies are
considering giving the eel “rare and endangered” status. More money is going toward
research for fish ladders over dams.


Marc Gaden is spokesman for the Great Lakes Fishery Commission.


“We’re committing ourselves, our resources to working to make the recovery of the
species a reality.”


The province of Ontario has closed the eel fishery in its waters for the foreseeable future.


(Sound up at beach)


Fisherman John Rorabeck supports that plan. He stares out across the waters he’s
trawled for decades. He says he’s behind anything to bring the eel back for future
generations.


“And hopefully we can, but I don’t expect to see it in my time. When I…[crying]…when I
think of all the times that we’ve had out in the lake and my forefathers and see what’s
happening here, it breaks you down.”


Rorabeck says when he thinks of the eel nearing extinction, he feels like he and his way
of life are becoming extinct too.


For the GLRC, I’m David Sommerstein.

Related Links

Study: Farm Chemicals Have Generational Effects

  • A new study exposed rats to common farm chemicals and found that the effect of the chemicals lasted multiple generations. (Photo by Tamara Bauer)

A first-of-its-kind study supports the theory that some common agricultural chemicals can cause reproductive problems that are passed down through generations. The Great Lakes Radio Consortium’s Erin Toner reports:

Transcript

A first-of-its-kind study shows some common agricultural chemicals can cause reproductive problems that are passed down through generations. The Great Lakes Radio Consortium’s Erin Toner reports:


In the study published in the journal Science, pregnant rats were exposed to high doses of two commonly-used chemicals: a fungicide used mainly by wine makers and a pesticide that replaced DDT.


The study showed the toxins caused low sperm counts in the rats’ male offspring down through four generations. Washington State University biologist Michael Skinner led the research team.


“This is a brand-new phenomenon; the fact that an environmental toxin can cause at all a multi-generational disease state, is something we didn’t know existed.”


Skinner stresses that the level of chemicals used in the study were above the level anticipated to be in the environment. But he says the research supports the idea that such toxins are causing permanent reproductive problems in men in some parts of the world.


For the GLRC, I’m Erin Toner.

Related Links

High Hopes for Whooping Crane Eggs

  • A baby whooping crane walks toward the camera. (Photo courtesy of the USGS)

Wildlife experts hope an experimental flock of whooping
cranes will lay more eggs this spring. The first egg produced during the experiment was recently found damaged. The Great Lakes Radio Consortium’s Chuck Quirmbach reports:

Transcript

Wildlife experts hope an experimental flock of whooping cranes
will lay more eggs this spring. The first egg produced during the
experiment was recently found damaged. The Great Lakes
Radio Consortium’s Chuck Quirmbach reports:


Scientists working on the project to develop 25 nesting pairs of
migrating whooping cranes in the eastern U.S. hope this is the year the
young cranes start to produce offspring.


But Michael Putnam of the
International Crane Foundation says one obstacle to the hatching of
crane eggs may be inexperienced parents.


“Once they do produce a fertile egg, then the birds have to exhibit the
right behaviors to tend the nest, incubate… and we’ve found some of
our birds- The females might be very good incubators at the
beginning, but it may take the male a year or two to catch on that’s
supposed to take a turn sittin’ on the egg.”


Putnam says other difficulties may include predators eating the eggs.
if the birds are successful, it’ll be the first whooping crane egg to
hatch in this part of North America in more than a century.


For the GLRC, I’m Chuck Quirmbach.

Related Links

Continuing Success for Migrating Whoopers

  • Whooping cranes are being successfully trained to migrate in the Midwest. (Photo courtesy of U.S. Fish and Wildlife Service)

An experimental flock of whooping cranes is starting to head back to the Midwest. Three birds died while down South over the winter. But later this year, the migrating cranes may start creating their own little replacements. The Great Lakes Radio Consortium’s Chuck Quirmbach reports:

Transcript

An experimental flock of whooping cranes is starting to
head back to the Midwest. Three birds died while down South over
the winter. But later this year, the migrating cranes may start creating
their own little replacements. The Great Lakes Radio Consortium’s
Chuck Quirmbach reports:


At least eight whooping cranes have either died or been injured
during the experiment to create a migrating flock of whoopers in the
eastern U.S. But Rachel Levin of the U.S. Fish and Wildlife Service
argues despite the losses, the experiment is going well.


“After 4 years of ultralight led journeys with whooping cranes, we have 45 wild
cranes now where just ten years ago east of the Mississippi we
had no wild whooping cranes.”


However the crane experiment remains unpredictable. Some of the
cranes may not come back to Wisconsin where they received their
migration training behind ultralight aircraft. Last summer, several of the
birds wound up in Michigan. Also some of the cranes may now be
sexually mature and scientists are eager to see if the migrating birds
produce their first offspring.


For the GLRC, I’m Chuck Quirmbach.

Related Links

Little Fish, Big Fish: Which to Keep?

The common practice of throwing the little ones back could be harming future fish populations. The Great Lakes Radio Consortium’s Christina Shockley reports:

Transcript

The common practice of throwing the little ones back could be harming future fish populations. The Great Lakes Radio Consortium’s Christina Shockley reports:


Anglers and commercial fisheries are often only allowed to take fish that are larger than a certain size. So the smaller fish are left to reproduce. And researchers say that means their offspring will also be smaller, and not as healthy.


David Conover is a marine scientist at Stony Brook University. He says the larger fish are vital to the overall health of their species.


“The eggs that these big, old females produce tend to be of higher quality. The egg diameters may be a little larger, the yolk that is supplied to the eggs seems to be more rich, the larvae hatch at a larger size, they have a higher survival.”


Conover says fish populations can be harmed in as little as three or four generations. And it can take much longer for a population to rebound – if it can at all.


He says possible solutions could include different rules that protect larger fish, and new limits on where fish can be harvested.


For the GLRC, I’m Christina Shockley.

Related Links

Study Reveals Coots Can Count

A new study in the journal Nature reveals that some birds can count. Researchers have found that they’re able to identify and tally their eggs in order to improve their reproductive success. The Great Lakes Radio Consortium’s Sarah Hulett explains:

Transcript

A new study in the journal Nature reveals that some birds can count. Researchers have found that
they’re able to identify and tally their eggs in order to improve their reproductive success. The
Great Lakes Consortium’s Sarah Hulett explains:


Bruce Lyon is a biologist at the University of California Santa Cruz. He made the discovery while
doing research on the reproductive behavior of American Coots. Coots are dark gray, duck-like
waterbirds that live in the northern U-S and southern Canada. They’re parasitic birds. That means
they lay some of their eggs in other coots’ nests – tricking the host birds into incubating eggs that
aren’t theirs.


But Lyon found that some females are able to recognize the foreign eggs by counting and ignoring
the imposters. Lyon says taking care of other birds’ eggs means a slimmer chance of their own
chicks surviving.


“There’s not enough food to go around, and if you end up raising somebody else’s chick, it
probably means you’ve lost one of your own.”


Lyon says a female coot will protect her babies by identifying eggs that aren’t her own, and burying
them or pushing them to the edge of the nest.


For the Great Lakes Radio Consortium, I’m Sarah Hulett.

Virgin Shark Birth Sets Researchers in Motion

  • Biologists are looking at how a shark in a Great Lakes region aquarium gave "virgin birth" last year. Photo courtesy of Belle Isle Aquarium, Detroit.

A female shark in an aquarium in the Great Lakes region has apparently given virgin birth. Four shark eggs hatched last year and three of those babies are now growing normally. As the Great Lakes Radio Consortium’s Celeste Headlee reports, it may be some time before the cause can be determined, but the event is still a surprise for biologists:

Transcript

A female shark in an aquarium in the Great Lakes region has apparently given virgin birth. Four
shark eggs hatched last year and three of those babies are now growing normally. As the Great
Lakes Radio Consortium’s Celeste Headlee reports, it may be some time before the cause can be
determined, but the event is still a surprise for biologists:

Biologists have a technical term for virgin birth. It’s called parthenogenesis. Doug Sweet is the
Curator of Fishes at the Belle Isle Aquarium in Detroit. He says parthenogenesis is common in
invertebrates and some amphibians.

“Most vertebrate animals, the females will produce eggs even if the male is not around. And it’s
just a matter of… it’s a chemical trick, basically, to get that egg to develop into an individual
without a sperm activating it.”

But parthenogenesis has been totally unheard of for sharks, until now. Last year, the Henry
Doorly Zoo in Omaha, Nebraska, announced they thought a Bonnethead shark there had
reproduced by parthenogenesis. The baby lived less than 12 hours, though, and genetic tests were
inconclusive.

But when Doug Sweet saw the press release from the Henry Doorly Zoo about a possible virgin
birth, he thought he’d try an experiment. Sweet decided to incubate the eggs of his two female
bamboo sharks. Four of the eggs developed. Sweet says the sharks were acquired by the
aquarium before they had reached sexual maturity, and they have never been exposed to a male.
He says the likely conclusion is that these sharks are reproducing by parthenogenesis.

Two other explanations, though highly unlikely, are that the shark has both testicular and ovarian
tissue, and fertilized its own eggs or that sharks are capable of storing sperm for years and even
passing it down to their offspring. Sweet has sent small clippings from the sharks’ fins to the
Henry Doorly Genetics Lab. Testing has already begun, but Sweet says it could take more than a
year to get the results. In the meantime, Sweet says the facts remain the same: a female shark
has given virgin birth. If it is parthenogenesis, he says, it will have important implications for
biologists around the world.

“Parthenogenesis just hasn’t been considered to happen in sharks; it’s never been recorded. It may
be happening all the time out there, so this is kind of breaking news in the shark world.”

The two adult bamboo sharks and the offspring are currently on exhibit at the Belle Isle
Aquarium in Detroit.

For the Great Lakes Radio Consortium, I’m Celeste Headlee.