Caviar Farming at Marshallberg Farm

Features - Cover Story

Discovering the secrets behind the farming of Osetra caviar — one of today’s rarest and most expensive delicacies.

July 31, 2019

Caviar farming is a slow process, taking seven to ten years before a juvenile fish matures and a female’s eggs are ready for harvest.
Bethany Barton

By Lisa Lupo

Photos by Bethany Barton

With 76 recirculating aquaculture system (RAS) tanks containing 35,000 sturgeon between two facilities, Marshallberg Farm is the largest Russian Sturgeon and Osetra caviar producer in North America. The two-site caviar farm has 40 indoor RAS tanks in about 54,000 square feet in Core Sound, N.C., and 36 in about 50,000 square feet at its LaPaz site just outside Lenoir, N.C. Each location houses the sturgeon in two buildings and has a separate facility for the staging, processing, and storing of its caviar and smoked sturgeon.

Such statistics would likely bring to mind a picture of an expansive operation with numerous workers and complex processing equipment. But that picture would be the antithesis of Marshallberg’s processing — which is conducted by hand at the two locations with Manager Sabine Mader commuting between the two.

In May, QA magazine visited Marshallberg’s LaPaz site to discover the secrets behind the farming of Osetra caviar — one of today’s rarest and most expensive delicacies. (See Saving Sturgeon from Extinction.)

CLEAN NOT CLEAR. Although some farms grow the sturgeon in outdoor ponds or tanks, Marshallberg uses only indoor tanks with a sustainable recirculating aquaculture system. The RAS filters the water first through a self-cleaning, rotating screen that removes the solids. Then the water runs through a biofilter to filter out the naturally released ammonia, nitrates, H3, and NO2. Solids are again filtered out, then the water is run through an oxygen box and recirculated back into the fish tanks. The 24/7 system uses well water, of which it recirculates 90%, losing only 10% through evaporation and the sludge collectors.

While the water needs to be kept clean, for fish, that’s not the same thing as being clear. It is natural for many fish species, including sturgeon, to live in waters rich in tannins, which helps cloak them from being seen from above. “The trick,” Mader said, “is to keep beneficial bacteria used for filtration happy and our fish happy at the same time.”

The tanks are all monitored with oxygen sensors. If it were to drop below the set level, an alarm would be triggered. “We set the level above what the fish would notice; but pumps do break occasionally, so we need to have preventive measures,” she said.

CAVIAR FARMING. Caviar farming provides a distinctive depiction of the circle of life, with the process beginning with the fertilized eggs of the sturgeon and finishing with the unfertilized eggs of caviar. And, like the circle of life for many animals, it is a slow process, taking seven to ten years before a juvenile fish matures and a female’s eggs are ready for harvest.

Humane handling throughout the process is a priority at Marshallberg. At every step from hatch to harvest, the welfare of the sturgeon is taken into consideration. This is not only good for the fish, it is essential to the quality of the final product. Caviar is expensive, not only because of the years to maturity (during which expenses are incurred for feed, liquid oxygen, and extremely high electric bills for the RAS system), but also because a sturgeon’s eggs come in only once a year in ideal conditions; in the wild, it can be two years between hatches. Additionally, a fish can resorb its eggs under stress or if it senses unfavorable conditions — adding another year before harvest can take place.

“If we were to put a fish with eggs in a tank where it was unhappy, it would resorb its eggs; just as a mammal that felt threatened would hold back birthing,” Mader said. Physical characteristics, such as lack of injuries, intact skin, and clear eyes, also provide proof of its health and welfare, she said.

Marshallberg is working on spawning its own fish eggs, but currently imports themfrom Germany. This means driving from North Carolina to the Atlanta airport, into which the fertilized eggs are flown, to pick them up and drive them back to North Carolina. The eggs hatch within a few days, and the fish are placed into a nursery tank — where they are given lots of space and are fed by hand.

When the fish reach about 600g in weight (just under a pound and a half), they are moved into larger tanks and fed every two hours from automatic robot feeders that drop the feed, specially formulated for sturgeon, to the bottom of the tank at specified intervals. Like Pavlov’s dog, the fish learn when the next drop is coming and congregate around the feed area. And like all life forms, the survival of the fittest applies, with the largest of this bottom-feeding species commandeering the bottom of the tanks.

The water flow and feed are set to provide as close to a natural environment as possible, and Marshallberg does not use any antibiotics or hormones. The fish stay in these tanks until the reach about 5kg (11 pounds).

The final step before harvest is the staging process, which involves an ultrasound of each mature fish to determine its sex and the maturation of a female’s eggs. Each fish is individually removed from the tank and placed on a specialized ultrasound table. If determined to be female, with eggs close to maturation, it is placed into a blue water-filled tub from which it then will be placed into a cleansing tank of very cold water.

The females stay in the cleansing tank for four to six weeks. At this point, they are no longer fed, to replicate their natural process of fasting in the months before spawning. The time in the now-clear waters of the cleansing tank also helps to clear the previous tank water from their systems to provide for the best quality of both the caviar and smoked sturgeon. Traffic in the staging building is also kept to a minimum to prevent stressing the sturgeon. With the clarity of the water, Mader said, “The fish can see us and know they are seen!”

After four to six weeks, a biopsy with a surgical hypodermic pipette is conducted to see if the eggs are ready. A Marshallberg-quality caviar egg will be about 2.5 mm with a “nice pop,” Mader said.

Marshallberg filters its water through a RAS system, recirculating 90% of the water and losing only 10% through evaporation and sludge collectors.
Bethany Barton
Bethany Barton
The caviar process begins with harvesting of the eggs after the female has been euthanized.
The roe is then separated from the tissue by gently massaging the mass over a screen.
Bethany Barton
Bethany Barton
The roe is rinsed with isotonic ice water in the bowl, then drained and rinsed several times.

CAVIAR PROCESSING. Marshallberg processes the caviar one fish at a time with two people, processing about eight fish per day. On the day of QA’s visit, Mader conducted the harvesting of the eggs and fileting of the meat, then worked with Caviar Processing Technician Lisa Lee on the processing of the caviar.

The process begins with harvesting of the eggs after the female has been euthanized. This and the fileting of the meat is conducted in one sterile room, with the eggs placed into a sterile metal bowl set on ice and passed through a window into a second room for cleaning, processing, and packaging. In addition to smoking the meat of both the females and males, Marshallberg sells as much as possible of the remaining byproducts:

  • Fashion purses can be made from the sturgeon skins.
  • The heads and fins are popular in Russian communities for traditional fish soups.
  • The bladder can be used for isinglass.
  • Male gonads find uses in cosmetics.
  • The pituitary glands are collected internally for future use in the induction of spawning.

While that leaves very little unused byproduct, Marshallberg Farm is continuously exploring more ways to utilize byproducts. “Meat trimmings for instance are high in omega-3 and would make an ideal animal feed ingredient,” Mader said, adding, “We hope to explore this in the future.”

Meanwhile, in the packaging room, Lee has written down the time the harvested eggs, or roe, is passed into the room and the weight before cleaning. The roe is then separated from the tissue by gently massaging the mass over a screen through which individual eggs fall into a clean metal bowl. “It is always done by hand,” Mader said. “I have not heard of a machine that can do this yet.”

The 42-pound sturgeon processed that day yielded about 4.7 pounds of eggs, which at 11% is fairly standard — a sturgeon can be expected to yield 10% to 14% of its weight in eggs. Once separated from the tissue, the roe is rinsed with isotonic ice water in the bowl, then drained and rinsed several times over a screen. Residual tissue and low-quality eggs are removed by hand with tweezers. Once thoroughly rinsed and dried, the eggs are scooped back into a metal bowl, and fine salt, at a quantity of 4.25%, is added. This is gently and thoroughly mixed by hand.

The eggs have now been transformed. “Now we can officially say it is caviar,” Mader said. “Before the salt was in there, it wasn’t caviar; it was eggs.”

Almost ready for packaging, the caviar is once again spread on a screen for a final drying and any last bits of tissue or low-quality eggs are picked out. The caviar is packaged first into bulk tins, with the eggs mounded well above the top of the tin, which will be lidded and weighted down to compress the caviar. “You don’t want any air in it, so you build it up and pack it in as you go,” Lee said. The bulk tins are aged in the cooler for four months with every batch numbered and labeled; and every lot number being that of a single fish.

Like fine wine, aging increases the quality of caviar. For this reason, the eggs are graded twice — at harvest and again after aging. Quality caviar, Mader said, should “burst in your mouth with a firm texture and have a buttery, nutty taste.” And, also like wine, “every batch is slightly different,” she said.

FOOD SAFETY. Marshallberg follows all applicable regulations, including Seafood HACCP and FSMA, but it also goes well beyond those. “FDA is helpful, but at the end of the day, we have to keep everything clean,” Mader said. “Everything we do here is streamlined and follows protocols, so it is 150% clean and safe.”

Temperature is so critical to the preservation of the caviar that it is a key food safety and quality focus. Though refrigeration can be as high as 38°F by regulation, Marshallberg keeps it at 28°F to 29°F. And it not only has back-up thermometers; its back ups have back ups. The coolers themselves have highly regulated thermostats, but a small temperature reader also is placed inside each cooler to verify the temperature. The device, reads the temperature every 15 minutes; then is pulled once a week with the temperature recorded and a report made of the over-time curve values.

Additionally, weekly validation is made of each temperature reader, with a master thermometer placed in ice water to verify its accuracy. The master then is set next to each small temperature reader to validate its accuracy. And if anything is off — there are plenty of back ups for replacement. The facility coolers also have two compressors, so if one goes down, the other will take over. But the compressors also are checked regularly to ensure proper operation.

Additional preventive measures include:

  • Every morning, the processing and packaging rooms are completely rubbed down with rubbing alcohol.
  • Utensils and bowls are used for only one fish, then cleaned before being used for another.
  • If an employee is sick, he or she is directed to stay home.

“A cascade of preventive measures makes mistakes within the process almost impossible,” Mader said. “If a mistake were to occur, the lot would most certainly be identified, located, and removed from the inventory immediately. Our first priority is product quality and safety.”

Consumer Education. Because of the delicacy of caviar, the greatest food safety and quality challenges actually come after it reaches the consumer. It is for this reason that Marshallberg provides as much education as possible through written instruction, verbal education (when the caviar is purchased by phone or at the local farmers’ market), and web links. This is important because the vacuum-sealed tin must refrigerated as soon as possible and be kept a temperature of 28°-38° F. Once opened, the caviar should be served in the tin or a dish on ice, and eaten within 24 hours.

Marshallberg is very open about its processes, even posting a video of caviar farming and processing on its website. Transparency is very important, Sabine said. “You know what you’re eating and what’s in it. We have no secrets.”

The author is the editor of QA magazine. She can be reached at