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How
Do They Harvest Caviar?
They
suck it through a straw.
By
Daniel Engber
Posted
Tuesday, Oct. 4, 2005, at 3:07 PM PT
As of last
Friday, the United States no longer permits the importation
of fancy beluga caviar from the Caspian Sea. The U.S. Fish and
Wildlife Service announced the ban as part of an effort to protect
endangered sturgeon near Azerbaijan, Iran, Kazakhstan, Russia,
and Turkmenistan. Do sturgeon die when fishermen take their
eggs?
Yep. Almost
all caviar is harvested from dead fish. Fishermen on the Caspian
wait until the mature female sturgeon (which are at least 10
years old) are ready to migrate upstream and lay their eggs.
Once caught, the sturgeon will be transferred to a large boat,
where workers slit her open and remove her eggs. The caviar
is cleaned to prevent spoilage and then packed up; the rest
of the fish is sold for flesh.
Why can't
the fishermen postpone the harvest until the sturgeon lays her
eggs? First of all, the eggs would be almost impossible to gather.
A female that's ready to spawn might be swollen with pounds
of black caviar clumped together on her ovaries. Once she releases
these eggs into the water, they're much harder to collect, clean,
and package.
Second,
there's no market for ovulated or fertilized fish eggs. When
the female begins to spawn, the exterior of her eggs deteriorates
to allow for the penetration of sperm. Even if fishermen were
able to sweep up those ovulated eggs, they wouldn't be able
to sell them: An egg with a broken-down lining will eventually
leak and turn to mush. (The quality of caviar depends on its
firmness, taste, color, and size.)
Fish farmers
who raise sturgeon for caviar sometimes use a surgical procedure
to remove eggs from a female without killing her. To foster
reproduction in captivity, aquaculturists will induce ovulation
in a female with hormone injections and then make a small incision
in her abdomen. Eggs that have already detached from the ovaries
can be scooped out with a plastic spoon or squeezed out into a bowl.
Most farmers
use this technique only to obtain eggs for insemination, but
some Russians do live-harvest eggs for food. In some cases,
a farmer might perform a Caesarean on a fish that hadn't ovulated.
He could cut out some but not all of her eggs before sewing up the fish and putting her back in the water.
A farmer might also induce ovulation, squeeze out the loose
eggs, and then use a novel process to restore the integrity
of their outer coverings.
Caviar producers
who harvest from dead animals can still use surgical techniques
to improve their yield. Some fisheries will test the eggs of
a mature female before killing her. First, an incision is made
in her abdomen and then a small tube is inserted. The farmer
then puts his mouth on the tube and sucks out a small quantity
of eggs for examination. If they're the right color and consistency,
he'll kill the animal and harvest the caviar. If they're too
"ripe"—if the fish has begun to break them down for reabsorption—he'll
put her back in the water and wait until her next reproductive
cycle.
Got a question
about today's news?
Ask the Explainer.
Explainer thanks Peter Struffenegger of Sterling Caviar,
Frank Chapman of the University of Florida, and Mark Zaslavsky
of Sturgeon AquaFarms.
Daniel Engber is a regular
contributor to Slate.
Photograph of caviar by Caren Firouz/Reuters/Corbis.
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