Key findings

• White Sturgeon are large fish native to North America and are often raised on farms for both caviar and meat, resulting in high profits for both. 
• Current stunning practices used during the harvest of white sturgeon are ineffective, inhumane, and time-consuming, reducing the animal welfare of sturgeon raised on farms. 
• Non-Penetrative Captive Bolt (NPCB) guns can make both juvenile and adult white sturgeon unable to feel pain or fear. This method should be considered a more humane alternative to traditional methods. 

The final step of fish and animal welfare is a humane death 

Animal welfare is often described as the quality of life for an animal, with “life” being the key word. However, welfare also includes the animal's death. Farmed fish are not held to the same standards of animal welfare as other animals. Often, fish welfare is overlooked entirely. For fish farmers, welfare is often assessed through the lens of water quality, an important factor for fish. However, water quality does not cover other important welfare aspects of fish culture, such as proper nutrition, space, and handling. Part of the reason fish welfare is not considered outside of water quality is a lack of available resources and research on fish welfare, especially at harvest. 

Harvesting, or preparing fish for market, is a stressful time for fish. Poor welfare practices contribute to unnecessary stress. Good animal welfare at harvest means that fish should be slaughtered (killed for human eating) humanely¹. For slaughter to be humane, animals must be stunned within 1 second of a stunning application. This means that animals are unable to feel fear or pain (insensible) before death occurs without a chance of recovery. Research shows that only two of the many legal methods of stunning fish are humane when performed appropriately. These two methods are percussive and electrical stunning. 

Percussive stunning, or blunt force trauma to the brain, is the method often used for farmed white sturgeon. The two-step slaughter process uses a stunning method, usually manual percussion, to make the fish insensible. This step is followed by cutting the gills and bleeding the fish out in an ice bath. The large size and cartilage skeleton of white sturgeon can be a challenge for farmers at harvest. White sturgeon and other sturgeon species often require multiple strikes to make them insensible. Alternative stunning methods could ensure that white sturgeon are effectively stunned and do not experience pain or fear before death². 

A more humane stun-and-slaughter protocol will protect and improve animal welfare for these fish during processing. 

In the United States and many other countries, there are no rules or regulations governing the welfare of fish at slaughter. Unfortunately, sturgeon are no exception. In this brief, I describe a recent study that tested an alternative stunning method for quickly and irreversibly making white sturgeon insensible before death. 

The importance of sturgeon in farming and society

White sturgeon are large fish native to North America that can live up to 60 years and reach lengths of over 14 feet. The United States has the second-highest total revenue from sturgeon production globally³. These fish are highly profitable because they are farmed for both meat and caviar. Caviar, or sturgeon eggs, is one of the most visible and high-profile farmed products globally. Caviar is often considered a luxury item. In 2018, farms across the United States produced around 60,000 pounds (27,200 kg) of caviar. It resulted in nearly $7.7 million in sales⁴. As the demand for white sturgeon and sturgeon products increases, commercial farms across the United States are working hard to increase production.

Figure 1: An adult white sturgeon swimming at the Monterey Bay Aquarium
Macrophyseter, CC BY-SA 4.0, via Wikimedia Commons.

Despite their high value, there is little research into white sturgeon welfare at harvest. A non-penetrative captive bolt gun (NPCB) may offer a humane and effective alternative to the traditional method of percussive stunning. NPCBs often use pressurized air to move a striking bolt with great force. These bolts can produce much higher levels of force than can be produced by a human. 

Finding effective bolt gun pressures for two sizes of sturgeon 

To test whether NPCB could be a humane stunning option, a study was conducted at Sterling Caviar, a white sturgeon farm in California. Pressures of 120, 135, and 145 pounds per square inch (PSI) were tested on 2–3-year-old juvenile white sturgeons, and pressures of 175, 200, and 225 PSI were tested on adult white sturgeons. Each pressure was used on three different white sturgeon of the same harvest size, with each receiving a single strike from an NPCB. 

Researchers checked whether the fish was insensible by observing jaw relaxation. Jaw relaxation is an indicator that an animal is no longer awake and cannot feel fear or pain. If jaw relaxation was seen, the white sturgeon moved to the second step of the slaughter process. The sturgeon were bled in an ice slurry and monitored for signs of recovery for an hour. 

After monitoring, researchers used a small saw to remove sections of cartilage containing the brain from these white sturgeon. Researchers sent the cartilage to the UC Davis Pathology lab to examine for tissue damage indicative of severe brain injury. Researchers found that NPCB caused significant brain tissue damage in juvenile white sturgeons but not in adults (Figure 2). Although tissue data for the traditional method is not available, NPCB can still be considered an improvement. NPCB can quickly make white sturgeon insensible with one strike.

Is one strike enough?

Researchers conducted a follow-up study at the same farm using the effective pressures determined in the previous study. An NPCB gun delivered strikes of 145 PSI to 100 juvenile sturgeons and 225 PSI to 65 adult sturgeons. Researchers checked each fish for jaw relaxation before bleeding in an ice slurry for two hours of monitoring.

None of the juvenile white sturgeon recovered in the ice slurry following the 145 PSI strike. A small portion (10%) of the adult white sturgeon recovered and needed another strike to be made insensible. Even though two strikes may be needed, NPCB is still considerably more effective than the traditional alternative at making white sturgeon insensible. 

Improved sturgeon welfare benefits everyone

Fish farming is one of the fastest-growing protein industries in the world, and the importance of ensuring good welfare practices should grow alongside it⁵. Because of increased research into humane slaughter practices for fish, we know that more humane practices result in higher-quality products for consumers and higher profits for producers⁶. Better harvest practices could ensure fish lose consciousness quickly and do not feel pain or fear before they die. 

Jennifer Bowman is a University of California, Davis Ph.D. candidate in the Animal Biology Graduate Group working under the advisement of Dr. Jackson Gross. Dr. Gross is the head of the Aquaculture Cooperative Extension Lab in the Department of Animal Science at the University of California, Davis, and conducted the research described.

¹ American Veterinary Medical Association AVMA, Guidelines for the Humane Slaughter of Animals: 2024 Edition (American Veterinary Medical Association, 2024); HSA, Captive-Bolt Stunning of Livestock (Humane Slaughter Association, 2013), 34, https://www.hsa.org.uk/downloads/publications/captiveboltstunningdownload.pdf.

² Jackson A. Gross et al., “Evaluation of Non-Penetrative Captive Bolt Stunning as a Method of Slaughter for White Sturgeon (Acipenser Transmontanus),” Frontiers in Animal Science 5 (June 2024).

³ FAO, “Fisheries and Aquaculture,” https://www.fao.org/fishery/en/statistics/software/fishstatj.

⁴ USDA National Agricultural Statistics Service, “2017 Census of Agriculture,” www.nass.usda.gov/AgCensus.

⁵ Food and Agriculture Organization, The State of World Fisheries and Aquaculture 2022 (FAO, 2022), https://openknowledge.fao.org/handle/20.500.14283/cc0461en.

⁶ Anders Kiessling et al., “Texture, Gaping and Colour of Fresh and Frozen Atlantic Salmon Flesh as Affected by Pre-Slaughter Iso-Eugenol or CO2 Anaesthesia,” Aquaculture 236, no. 1 (2004): 645–57; David P. Green, “Sensory Evaluation of Fish Freshness and Eating Qualities,” in Cesarettin Alasalvar et al. (eds.), Handbook of Seafood Quality, Safety and Health Applications (Oxford: John Wiley & Sons, Ltd, 2010); Jucilene Braitenbach Cavali et al., “Pre-Slaughter Stunning Methods Influence the Meat Quality of Arapaima Gigas Fillets,” Animals 14, no. 8 (2024): 8.