[env-trinity] Scientists breed smelt in case species becomes extinct in Delta

Tue Apr 1 10:52:03 PDT 2008

Scientists breed smelt in case species becomes extinct in Delta

By Matt Weiser - mweiser at sacbee.com 

Last Updated 6:04 am PDT Monday, March 31, 2008
Story appeared in MAIN NEWS section, Page A1

http://www.sacbee.com/101/story/823346.html 

<http://media.sacbee.com/smedia/2008/03/30/20/195-1W31SMELT1.standalone.
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Juvenile Delta smelt that are being bred as a refuge population of the
endangered fish swim in a beaker at the UC Davis Fish Conservation and
Culture Laboratory earlier this month near Byron. The fish will require
several months of a steady diet of tiny shrimplike animals before they
reach their adult size - about the length of a finger. Randy Pench / 
rpench at sacbee.com 

See additional images
<http://www.sacbee.com/101/story/823346.html#more_images> 

BYRON - Inside a makeshift collection of modified shipping containers
lined up on a patch of asphalt, a system of gurgling pipes and buckets
holds the Delta's future. Or, at least, one future.

These faded steel boxes house the beginnings of a new refuge population
of threatened Delta smelt. The fish, only finger-length at adulthood,
could be used one day to restore the population if their wild kin go
extinct.

Unfortunately, extinction is all too likely after five years of steep
population declines for the smelt and four other fish species in the
Sacramento-San Joaquin Delta. All are known as "pelagic" fish because
they live in the Delta's moving water column. 

Scientists have been unable to explain the decline, much less solve it.
So the refuge smelt are intended as a last-ditch effort to save the
species, long considered a bellwether for the health of the estuary as a
whole.

If the smelt disappear, scientists believe, other species will follow,
along with a decline in water quality that could make Delta water
undrinkable for the 25 million Californians who depend on it.

Smelt, in other words, are the lead car in an ecological train that's in
danger of derailing.

"It's bigger than smelt," said Bradd Baskerville-Bridges, a marine
biologist and co-director of the UC Davis Fish Conservation and Culture
Laboratory, where the smelt are being raised. "It's affecting all the
pelagic species right now, and there's no easy solution."

The lab has been breeding smelt for 15 years for research purposes, so
scientists can learn more about how the fish respond to changing
environmental conditions. But the new refuge population, which started
breeding in December, has added new layers of rigor and importance to
the operation.

The process is like a very specialized fish hatchery, but miniaturized.
And it's a hands-on process.

Eggs and sperm are extracted by gently holding each tiny smelt in the
fingertips and firmly squeezing the abdomen from head to tail. The
female releases a nickel-sized puddle of eggs that resembles melted
butter. The male excretes a droplet of clear sperm gathered up in a tiny
suction device called a micropipette.

After mixing, the fertilized eggs are held in clear tubes about 3 inches
in diameter hanging inside one climate-controlled shipping container.
Each tube holds layers of fine, sandy sediment through which water is
constantly pumped from bottom to top.

The eggs cling to the sediment with a flexible foot, not unlike a
mushroom. After eight to 10 days, they hatch into tiny embryos to form a
swirling cloud that, on first glance, resembles the foam in a mug of
beer. Then you realize the cloud actually consists of about 5,000 baby
smelt.

Eventually the embryos respond to light and rise to the surface of each
tube, where they are drawn off into buckets to grow into juvenile fish,
each ghostly transparent and no longer than a fingernail.

It then takes several months on a steady diet of tiny shrimplike animals
- also raised at the lab - before the smelt reach adulthood.

"They're dependent on you like babies," said Sophie Wan, a laboratory
assistant supervising the juvenile smelt. "To be working with a fish
that's so close to being extinct is really interesting. It's important.
People don't know how important it is."

The lab is creating the refuge population from a parent generation of
just 500 smelt gathered from the Delta in December 2006. These are the
last wild fish the lab was able to obtain before officials halted
scientific collections in the Delta - another drastic step taken to
protect the species.

These parents will produce about 5,000 young for the first generation of
refuge fish, which must be tracked as individuals to ensure their
genetic diversity is maintained when they become parents of the next
generation in 2009.

That means more tubes, buckets and tanks.

State agencies recently contributed $2.1 million toward the effort to
hire more people for the project and expand the facility into a nearby
warehouse, expected to be ready in April.

There are currently no plans to reintroduce these fish. In fact, almost
no one wants that to happen yet. At the moment, they represent only a
backup plan.

Yet it's vital to ensure diversity in the refuge fish so that if they
are reintroduced, they will behave like wild fish and not compromise any
remaining in the wild.

So in addition to all the breeding steps, the lab now uses tiny scissors
to take a fin clip from each male and female parent. These are stored in
a color-coded vial for each fish - red for girls, green for boys - and
shipped to researchers on the UC Davis campus for genetic analysis.

Scientists believe a variety of factors have contributed to the smelt's
decline, including excessive water exports from the Delta to Southern
California, water pollution, and invasive species that outcompete smelt
for food.

Research using fish raised at the lab has shown that smelt feeding and
movement depend on narrow salinity and water flow requirements. This is
especially true when the fish are tiny juveniles, unable to control
their own movement in the Delta's strong currents.

The fish essentially evolved to thrive in the natural ebb and flow of
the Delta's rivers and tides, a pattern dramatically altered by the dams
and pumps that now govern the estuary.

Before reintroducing refuge smelt, scientists also need to be sure the
environment is ready for them. Otherwise, these fish might meet the same
fate as their wild cousins, which appear unable to thrive in the altered
water chemistry, temperature and runoff that exist now.

"It's because of human influences that these changes have occurred, so
it's up to us to rectify it," said Joan Lindberg, an ecologist and
co-director of the lab. "We haven't been the best stewards of the Delta.
So there should be a lot of effort to understand that and manage it so
it's more like a natural system."

About the writer:

*	Call The Bee's Matt Weiser, (916) 321-1264.

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Randy Pench / rpench at sacbee.com The eggs that will produce part of the
refuge population of the endangered Delta smelt are gathered in a dish
at the UC Davis Fish Conservation and Culture Lab near Byron earlier
this month. 

Click on photo to enlarge
<http://media.sacbee.com/smedia/2008/03/30/20/150-1W31SMELT2.standalone.
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