Sturgeon are considered to be ancient fishes, and the family they belong in (the Acipenseridae) dates back to some 200 million years ago. Much of their skeletal structure is made up of cartilage rather than bone, and their bodies are covered with large, bony, modified scales known as scutes. There are 27 living species of sturgeon today, all of which are found in the northern hemisphere, with eight species occurring naturally in North America.
Most sturgeon species are long-lived, and some do not mature until 15 to 20 years of age. Even the smallest species can reach weights approaching 50 lb., and the largest can weigh up to 800 lb. Some species can live to be up to 100 years old.
Typically feed on the bottom, so their natural diet includes crustaceans, mollusks, aquatic insects and other benthic invertebrates. With some exceptions, most sturgeon species are anadromous, with spawning and early life stages occurring in rivers, followed by growth in coastal freshwater or marine habitats, and then migration up rivers to spawn upon reaching maturity. Some species may spawn many times over the course of their lives.
Throughout North America, Native Americans fished for sturgeon species in their territories, but the harvests were sustainable and when European settlers arrived sturgeon were still plentiful across the continent. And while at that time sturgeon were considered to be reserved for aristocrats and royalty and off limits to commoners in Europe, the colonizers soon began to exploit the American populations. Apart from their meat, oil and skin, sturgeon were severely overfished for their roe, which was used to produce caviar.
During the 1900’s many populations declined rapidly, with some approaching extinction. For a time in the late 1900’s most wild sturgeon and caviar found in global trade came from the Caspian Sea. Government hatcheries in Russia and Iran stocked large numbers of sturgeon into the Caspian year after year to support harvests, but with the collapse of the Soviet Union the fishery became unregulated and populations were rapidly decimated. Sturgeon farming has helped reduce illegal fishing pressure on wild populations, but the problem persists.
Although fishing for most sturgeon species in the U.S. is now prohibited or strictly regulated, other threats to their long-term survival include dams on rivers, pollution, dredging activities, boat traffic, climate change and harmful algal blooms caused by agricultural and municipal run-off. Globally, the same threats have resulted in many other sturgeon species being classified as threatened or endangered in recent years. As a result, artificial propagation of sturgeon is now commonplace and sturgeon aquaculture occurs in more than 30 countries, including the U.S., but international trade in sturgeon products requires permits under the U.N.’s Convention on International Trade of Endangered Species (CITES).
A number of sturgeon species are cultured in the U.S., including the native White sturgeon (Acipenser transmontanus) and Atlantic sturgeon (Acipenser oxyrinchus), as well as several foreign species from Asia and Europe. Production operations focus on both meat and caviar production, with distinct production strategies for each product. While caviar is the high revenue product, meat sales and by-products such as isinglass also contribute to profitability.
Most sturgeon production in the U.S. involves the White sturgeon, which is native to the Pacific coast from Ensenada, Mexico to Alaska (although spawning does not take place south of the Sacramento – San Joaquin river system). The White sturgeon is the largest freshwater fish found in North America. In a survey of caviar production conducted associated with the World Sturgeon Conservation Society, the White sturgeon accounted for 12% of global supplies. Production protocols outlined here are based on White sturgeon culture and may vary, but only slightly, for other species.
When starting from fingerlings, the first eggs may be available as early as 7 years of age but in some cases not until 11 years have passed. In the wild and in farm operations, females may spawn every 2 to 4 years once they reach maturity. Hatchery methods generally involve stripping eggs and milt, fertilizing them artificially, treating the eggs to remove their natural adhesiveness and incubating fertilized eggs using hatching jars.
Fry are not well developed upon hatching, and early survival can be low during the feed training process. Once fish are actively feeding, growth is largely dependent on temperature and diet quality. Early growth phase diets are typically around 50% protein, decreasing over time to 30% to 35% protein. High lipid levels are also used, from 8% to 25%. Fish are grown to a size of 5+ kilograms, at which point sex can be determined using ultrasound equipment. Depending on farming conditions and management, this may take as little as 3 years. At this time, males are segregated for subsequent harvest for meat, while females are raised to maturity for caviar production.
Although sturgeon are generally hardy fish once they begin the grow-out phase of production, environmental and handling stress can trigger some disease outbreaks. Sturgeon seem to be particularly susceptible to viral diseases following stressful conditions. Care should be taken to use virus-free brood stock and fingerlings when establishing a captive population, and general biosecurity measures should be standard practice in any fish farm.
Optimal diet formulations for female egg production include significant portions of lipids from marine species. Once a female sturgeon approaches maturity, roughly 8% of her total weight will be eggs. Females with advanced ovarian development are transferred from comparatively warm waters in grow-out tanks to cold water holding facilities during the fall, where they are subsequently overwintered through the winter months. This period of cold temperatures is required for final egg maturation, at which point the ovaries may account for 15% or more of the total weight. Caviar production traditionally uses pre-ovulated eggs, and many operations sacrifice females to obtain pre-ovulated ova. Other operations, however, take ovulated eggs surgically through small incisions, so as to maintain viable female stocks that can produce eggs every two years, but this process is somewhat more difficult and may reduce the quality of the resulting caviar.
The 2018 USDA Census of Aquaculture indicated a total of 18 sturgeon farms were in operation in the U.S. at that time. Sixteen reported sales of food size fish, while two sold stockers for on-growing. One operation also reported sales of brood fish. Total combined sales were $10,318,000 and food size fish sales accounted for $8,039,000. California led the nation with 7 sturgeon farms, followed by Idaho with 5, Hawaii with 3, Florida with 2 and North Carolina with 1. California also led in sales, accounting for over 85% of the total value. A number of sturgeon operations also reported production of fish and fingerlings for conservation, recreation, enhancement and restoration purposes.
When establishing a sturgeon farm, sustained production will require initial access to fingerlings and/or breeding stock. Both will probably be difficult to obtain, although some sturgeon farms will sell juvenile fish into local live markets. In almost every scenario, a new sturgeon farming operation will need to maintain both healthy fish and functioning facilities for a number of years before generating any sales revenue. This results in a long window of risk exposure, including economic risks due to the high costs associated with raising these fish.
Meat sales will usually provide the first revenues for a start-up operation. Once fish are old enough to sex, males can begin to be harvested for meat. Wholesale distribution may be a straightforward market outlet, but opportunities are also available to produce value added products such as smoked fillets. By-products from slaughtered fish can also generate cash flow prior to the onset of caviar production.
Paying attention to the details of caviar production will be critical when entering the market for the first time. Eggs must be properly harvested, properly cleaned and salted, properly chilled and properly packaged and stored. Caviar consumers are discriminating, so quality aspects will directly impact business success.
Raising any sturgeon species anywhere outside of its natural range will require permission from regulatory authorities, and procedures vary from state to state. Raising a sturgeon species where it does occur naturally also requires a number of permits and licenses, but these are more easily obtained in some locations.
Currently, there is no shortage of markets for caviar. Demand from Europe, Asia and North America has historically been strong, but caviar is perceived as a luxury item and the pandemic-related economic downturn may dampen demand for some period of time. Prior to the pandemic, production was increasing more rapidly than demand, with many industry observers predicting an eventual drop in market prices for both caviar and meat. While U.S. represents largest caviar market globally, production is increasing rapidly in China and some other countries, suggesting imported products will impose downward price pressure for U.S. and European producers in the coming years.
Prepared by C. Greg Lutz, Louisiana State University Agricultural Center