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Sturgeon: The Fish with “Golden Eggs”

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By Milthon Lujan

Sturgeons are a group of primitive fish that have existed for millions of years. They are renowned for their prized caviar, one of the world’s most expensive foods. Sturgeons also play a significant role in aquatic ecosystems and face increasing threats due to overfishing and habitat loss.

Currently, aquaculture produces more hybrid species as a response to the rapid decline in wild sturgeon populations (Raposo et al., 2023), which has endangered various sturgeon species worldwide. Sturgeon aquaculture helps meet the exclusive global caviar market demand.

In this article, we aim to delve into the world of sturgeon, introducing you to well-known sturgeon types, sharing cultivation experiences, and highlighting conservation efforts.

What is a Sturgeon?

Sturgeons possess unique anatomical characteristics that distinguish them from other fish. They typically have a subcylindrical body, an extended and tough snout, and a ventrally protrusible mouth with barbels.

These fish have bony plates covering their heads. Some species can reach lengths of 2-3 meters.

Sturgeons are long-lived, with a potential lifespan of up to 100 years. They also exhibit slow growth, with some species taking up to 20 years to reach sexual maturity.

The taxonomic classification of sturgeons is as follows:

  • Kingdom: Animal
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Acipenseriformes
  • Family: Acipenseridae

Sturgeons belong to the family Acipenseridae, comprising 27 species, of which 4 are extinct. The remaining 23 are grouped into four genera: Huso (2 species), Scaphirhynchus (2 species), Pseudoscaphirhynchus (3 species), and Acipenser (16 species).

Types of Sturgeon Fish

There are 27 sturgeon species worldwide, distributed in the rivers and oceans of North America, Europe, and Asia. Some of the most common sturgeon species include:

  • White Sturgeon (Acipenser transmontanus): The largest freshwater fish in North America.
White Sturgeon (Acipenser transmontanus). Source: Oregon Department of Fish & Wildlife
White Sturgeon (Acipenser transmontanus). Source: Oregon Department of Fish & Wildlife
  • Beluga Sturgeon (Huso huso): The world’s largest freshwater fish, it can reach a maximum weight of 1,000 kilograms (Hung, 2017). The Beluga Sturgeon is native to the Black, Caspian, and Azov Seas.
Beluga Sturgeon (Huso huso). Source: Максим Яковлєв
Beluga Sturgeon (Huso huso). Source: Максим Яковлєв
  • Giant Sturgeon (Huso dauricus): A critically endangered species found in the Amur River in Russia and China.
Giant Sturgeon (Huso dauricus) at the Asamushi Aquarium in Aomori Prefecture, Japan. Source: Aomorikuma.
Giant Sturgeon (Huso dauricus) at the Asamushi Aquarium in Aomori Prefecture, Japan. Source: Aomorikuma.
  • Atlantic Sturgeon (Acipenser oxyrinchus): An endangered species found on the East Coast of North America.
Atlantic Sturgeon (Acipenser oxyrinchus) at the Montreal Biodome, Quebec, Canada. Source: Cephas
Atlantic Sturgeon (Acipenser oxyrinchus) at the Montreal Biodome, Quebec, Canada. Source: Cephas
  • Paddlefish Sturgeons (Pseudoscaphirhynchus kaufmanni, P. hermanni, and P. Fedtschenkoi): The smallest sturgeons inhabiting the Aral Sea, with a maximum weight of 0.5 kg.
Paddlefish Sturgeon (Pseudoscaphirhynchus hermanni). Source: Alexey Chernyak.
Paddlefish Sturgeon (Pseudoscaphirhynchus hermanni). Source: Alexey Chernyak.

Distribution and Habitat

Sturgeons inhabit a variety of marine and freshwater habitats worldwide. They are native to the Atlantic, Pacific, and Indian Oceans, as well as the Caspian and Black Seas.

Sturgeons are anadromous fish, meaning they spend part of their life in freshwater and part in saltwater. They typically spawn in freshwater rivers and streams and spend their adult lives in the ocean.

What Do Sturgeons Eat?

Sturgeons feed on the bottom and consume a variety of invertebrates, including worms, clams, and shrimp.

Hung (2017) describes that sturgeons are excellent bottom feeders because they have highly sensitive barbels on the lower snout to detect bottom-dwelling animals and a long, protruding mouth for suction-feeding their prey.

Sturgeon Caviar

Sturgeon caviar refers to the eggs of female sturgeons. It is considered a delicacy and is one of the most expensive foods in the world.

Caviar is produced by harvesting sturgeon eggs, which are then cured in salt and can be consumed raw, cooked, or used in a variety of dishes.

There are various types of caviar, each produced from a different sturgeon species. The most expensive caviar comes from the Beluga sturgeon, found in the Caspian Sea.

Caviar prices can vary widely, depending on the sturgeon species, caviar quality, and market conditions. Beluga caviar can be sold for up to $25,000 per kilogram. According to Lopez et al., (2020), the most famous and valuable caviars are the so-called Beluga from H. huso, Osetra from A. gueldenstaedtii, and Sevruga from A. stellatus and A. persicus.

Sturgeon Aquaculture

Sturgeon aquaculture is the practice of breeding sturgeons in captivity. It is a growing industry, providing a sustainable source of caviar. The decline in natural sturgeon populations, coupled with high caviar demand, has led to the development of sturgeon farming, primarily for caviar production (Bronzi and Rosenthal, 2014; Vasilyeva et al., 2019).

According to Vasilyeva et al., (2019), there are two trends in sturgeon aquaculture: controlled breeding for release (repopulation of natural populations) and commercial farming.

The high feed conversion ratio and growth rate, along with relative ease of cultivation, may lead the industry towards more specialized roles (Lobanov et al., 2023). Advances in aquaculture technology have made successful captive sturgeon breeding possible, with experiments even involving all-female populations to optimize caviar production.

Raposo et al., (2023) report that the main species used in aquaculture include Siberian sturgeon (Acipenser baerii), Russian sturgeon (Acipenser gueldenstaedtii), and White sturgeon (Acipenser transmontanus), while Lobanov et al., (2023) highlights that exploiting sturgeon tolerance to a wide range of salinity, pH, and dissolved gases suggests potential benefits from using marginal aquifers unsuitable for other purposes.

Breeding Systems

Elhetawy et al., (2020) evaluated the growth, maturity, and caviar quality in Russian sturgeons (Acipenser gueldenstaedtii) raised in recirculation systems or cages, concluding that:

a. Sturgeon meat production: recirculation technology was the most effective.

b. A combined application of recirculation systems/cages in Russian sturgeon farming could lead to shorter puberty, improved caviar quality, increased egg percentage, and larger oocyte size.

It is important to note that the depth and diameter of tanks in recirculation systems in aquaculture affect the growth of Chinese sturgeon (Acipenser sinensis), as reported by Zhang et al., (2022).

Dediu et al., (2021) evaluated the potential of hybrid juveniles of bester x beluga for intensive production in recirculation systems, reporting better results at low densities for the hybrids.

Sturgeon Genetics

Song et al., (2022) studied genetic parameters of Russian sturgeon (Acipenser gueldenstaedtii) for growth and egg-related traits, indicating that these traits could be improved through selection. Bestin et al., (2021) estimated genetic parameters for caviar production and quality traits (size, color, and firmness) in Siberian sturgeon A. baerii.

Heiner et al., (2020) reported the discovery of a molecular marker for sex determination in sturgeon, which could facilitate fish reproduction.

Sturgeon Feeding

Caimi et al., (2020) reported that up to 25% of fishmeal could be replaced with black soldier fly larvae meal (Hermetia illucens) in the diets of Siberian sturgeon (Acipenser baerii) juveniles without affecting reproduction.

Captive Sturgeon Reproduction

Mohammadzadeh et al., (2021) tested the biological function of recombinant gonadotropin-releasing hormone-associated peptide (rGnRH) for ovulation induction and spawning in Sterlet sturgeon (Acipenser ruthenus) breeders. The results showed that rGnRH at a dose of 10 μg kg PC-1 was the most efficient in inducing spawning.

On the other hand, scientists studied the reproduction strategies of the Chinese sturgeon (Acipenser sinensis).

Sturgeon Diseases

Like other aquaculture species, sturgeon farming faces the challenge of diseases. In this regard, Mugetti et al., (2020) has published an extensive scientific review describing viral diseases affecting different sturgeon species.

Sturgeon Conservation

Sturgeons face various threats, including overfishing, habitat loss, and pollution. Overfishing is the most severe threat, leading to the decline of many sturgeon populations. Sturgeons are listed as vulnerable, endangered, or critically endangered on the IUCN Red List of Threatened Species.

Sturgeons are also threatened by habitat loss, as spawning rivers and streams degrade due to pollution and development.

Conservation efforts are underway to protect sturgeons, such as in the Ebro River to recover the European sturgeon (Acipenser sturio) population. These efforts include fishing regulations, habitat restoration, and captive breeding programs. However, regarding captive breeding and subsequent release, Anderson et al., (2022) highlights that while aquaculture can be a valuable conservation and recovery tool, it is particularly effective when considering impacts on phenotypic development during the early life history and combined with effective post-release monitoring and additional restoration efforts.

Conclusion

Sturgeons are fascinating and crucial fish that play a vital role in the marine ecosystem. They face various threats, but conservation efforts are being made.

On the other hand, the aquaculture industry has seen sustained growth in recent years, mainly focused on caviar production. Hybrid development has facilitated aquaculture growth, and production is expected to continue increasing in the coming years.

References

Anderson, W. G., Schreier, A., & Crossman, J. A. (2022). Conservation aquaculture—A sturgeon story. In Fish Physiology (Vol. 39, pp. 39-109). Academic Press.

Bestin, A., Brunel, O., Malledant, A., Debeuf, B., Benoit, P., Mahla, R., … & Haffray, P. (2021). Genetic parameters of caviar yield, color, size and firmness using parentage assignment in an octoploid fish species, the Siberian sturgeon Acipenser baerii. Aquaculture, 540, 736725.

Bronzi, P., & Rosenthal, H. (2014). Present and future sturgeon and caviar production and marketing: A global market overview. Journal of Applied Ichthyology, 30(6), 1536-1546.

Caimi, C., Renna, M., Lussiana, C., Bonaldo, A., Gariglio, M., Meneguz, M., … & Gasco, L. (2020). First insights on Black Soldier Fly (Hermetia illucens L.) larvae meal dietary administration in Siberian sturgeon (Acipenser baerii Brandt) juveniles. Aquaculture, 515, 734539.

Dediu, Lorena, Angelica Docan, Mirela Creu, Iulia Grecu, Alina Mogodan, Marilena Maereanu, and Lucian Oprea. 2021. “Effects of Stocking Density on Growth Performance and Stress Responses of Bester and Bester × Beluga Juveniles in Recirculating Aquaculture Systems” Animals 11, no. 8: 2292. https://doi.org/10.3390/ani11082292

Elhetawy, A. I., Vasilyeva, L. M., Lotfy, A. M., Emelianova, N., Abdel-Rahim, M. M., Helal, A. M., & Sudakova, N. V. (2020). Effects of the rearing system of the Russian sturgeon (Acipenser gueldenstaedtii) on growth, maturity, and the quality of produced caviar. Aquaculture, Aquarium, Conservation & Legislation, 13(6), 3798-3809.

Hung, S. S. (2017). Recent advances in sturgeon nutrition. Animal Nutrition, 3(3), 191-204.

Lobanov, V. P., Pate, J., & Joyce, J. (2023). Sturgeon and paddlefish: Review of research on broodstock and early life stage management. Aquaculture and Fisheries.

Lopez, A., Vasconi, M., Bellagamba, F., Mentasti, T., & Moretti, V. M. (2020). Sturgeon meat and caviar quality from different cultured species. Fishes, 5(1), 9.

Mohammadzadeh, S., Yeganeh, S., Moradian, F., Milla, S., & Falahatkar, B. (2021). Spawning induction in Sterlet sturgeon (Acipenser ruthenus) with recombinant GnRH: Analysis of hormone profiles and spawning indices. Aquaculture, 533, 736108.

Mugetti, Davide, Paolo Pastorino, Vasco Menconi, Claudio Pedron, and Marino Prearo. 2020. “The Old and the New on Viral Diseases in Sturgeon” Pathogens 9, no. 2: 146. https://doi.org/10.3390/pathogens9020146

Raposo, António, Hmidan A. Alturki, Rabab Alkutbe, and Dele Raheem. 2023. “Eating Sturgeon: An Endangered Delicacy” Sustainability 15, no. 4: 3511. https://doi.org/10.3390/su15043511

Song, H., Xu, S., Luo, K., Hu, M., Luan, S., Shao, H., … & Hu, H. (2022). Estimation of genetic parameters for growth and egg related traits in Russian sturgeon (Acipenser gueldenstaedtii). Aquaculture, 546, 737299.

Vasilyeva, L. M., Elhetawy, A. I. G., Sudakova, N. V., & Astafyeva, S. S. (2019). History, current status and prospects of sturgeon aquaculture in Russia. Aquaculture Research, 50(4), 979-993.

Zhang, H., Jiang, N., Zhang, Y., Zhang, Y., Ni, Q., & Fan, Y. (2022). Effects of tank diameter and water depth on growth performance, antioxidant capacity and immune response of Chinese sturgeon Acipenser sinensis in recirculating aquaculture system. Journal of Applied Ichthyology, 38(1), 84-92.