Along the banks of the Caspian Sea, fishermen hawk tins of caviar and thick cuts of beluga sturgeon. Unfortunately, most of it is black-market fare — illegally harvested and traded.
Despite strict regulations, the vulnerable — and valuable — sturgeon has been greatly overfished and is on the endangered list in many parts of the world.
Barbara Rasco, professor in WSU’s School of Food Science, is among those working to help save the sturgeon in an international effort that could provide spin-off benefits for aquaculture in the Pacific Northwest.
Idaho white sturgeon
In 2005, the U.S. Fish and Wildlife Service voted to restrict the import of beluga sturgeon products from the Caspian Sea, citing concerns over unsustainable harvesting methods. Global demand for caviar — primarily from the United States — continues to exceed the supply, however, fueling the black market trade.
Rasco believes one answer to the problem is to promote U.S. sturgeon production — especially the fledgling white sturgeon industry taking shape in southern Idaho.
(A green sturgeon is native to the Pacific Northwest)
To this end, Rasco is collaborating with scientists — including graduate and undergraduate students — from Washington, Idaho, Montana, California and Oregon to investigate the reproductive biology of the sturgeon.
Relatively little is known about this aspect of the ancient fish — one of the oldest species on record and sometimes known as “living fossils.”
The project is being funded by grants from the Western Regional Aquaculture Consortium and Aquaculture Washington Idaho. Rasco hopes to develop technical information that will not only help conserve global sturgeon populations but will also provide U.S. sturgeon growers with new tools to produce and market caviar.
When the time is ripe
“It is an important project,” said Rasco. “If we are going to harvest the fish, we should make the highest and best use of them and sell them for the best price.”
One of the team goals is to develop a faster and less invasive method for predicting maturity in white sturgeon in order to optimize the yield and quality of harvested caviar — aka fish eggs or roe.
“We are in contact with scientists in Russia, Azerbaijan and Iran,” she said. “We are all trying to solve the same problems … and share information and good ideas.”
(Sturgeon and caviar are sold on the black market at an outdoor bazaar in Azerbaijan)
In the wild, slow-growing sturgeon do not mature until they are at least 10 years old. In captivity, they can mature within seven years. Large sturgeon can produce up to 100 pounds of eggs.
Traditionally, the only way to tell if the eggs are ready to harvest has been to “grab the fish from the water, make an incision and examine the eggs” according to Rasco.
This involves a combination of visual inspection and measurement of the oocyte polarization index, which reveals how far along the egg is in the development process.
“If we have to take the fish out of the water, we’d rather be able to take a blood sample, or scales or urine …something less stressful than doing a biopsy to predict where she is in the reproductive cycle,” saidRasco.
(Javier Linares-Casenave, University of California Davis, conducts a biopsy on a sturgeon for the project at the northern California fish farm of the Sterling Caviar company)
Ultrasound and blood work
The wide-ranging research team is trying to do just that. Led by investigators at Montana State University and evaluating samples sent from Sterling Caviar in California, the team is developing four promising new diagnostic tests.
Two of the tests — radioimmunoassay and Fourier transform infrared spectroscopy — require blood samples to measure plasma hormone or protein levels.
The other tests are less invasive — using ultrasound or short wavelength near infrared spectroscopy to monitor the development of the eggs through the body wall of the fish.
Looking toward the future, Rasco believes the team will come up with a more reliable test for determining when to harvest fish roe. But more important, she said the project will provide information on the reproductive biology of sturgeon that people worldwide can use to manage their fisheries.
Still an ancient mystery
Sturgeon were an important food source along the east and west coasts of the United States until the early 20th century.
“People mostly ate the meat,” said Barbara Rasco, professor, School
of Food Science. “They used to give the caviar away in bars in New York City.”
of Food Science. “They used to give the caviar away in bars in New York City.”She said so much caviar was available in the Hudson River drainage in the early 1900s that it was packed in 50-gallon drums. Ultimately, this overfishing heyday resulted in severely reduced populations, leaving many of today’s sturgeon on the threatened or endangered species lists.
(A large can of legal caviar typically sold in the U.S. and elsewhere to retailers who repackage it in tiny containers)
Despite its culinary appeal, the ancient sturgeon remains mostly a mystery to biologists. Sturgeon, whose relatives first appeared in the fossil record nearly 200 million years ago, are a “very primitive, evolutionary conserved” species, according to Rasco.
These toothless, partially anadromous fish spawn in fresh water and may also spend part of their life cycles in brackish estuaries — sometimes migrating along coastlines in Eurasia and North America. No natural species are found south of the equator.
Sturgeon are bottom feeders and can range from 7 to 20 feet in length and weigh up to 2,000 kg. They are a slow-growing species but some have a reported lifespan beyond 100 years.
To learn more about Rasco’s research, visit http://impact.wsu.edu/people/rasco.htm.
