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The welfare of sturgeon farmed for caviar

High in the mountains in the Spanish Pyrenees sits a fish farm. Here, sturgeon are kept in barren concrete tanks that are left out in the open. Visitors can ask for the animals to be fished out and lifted onto the tarmac for them to snap a photograph. It is obvious from the fish’s rapid gill movements that it is distressed due to the exposure to air. 

This is Nacarii Caviar, an award-winning producer of cured sturgeon eggs, more commonly known as caviar. Having been historically costly to produce, these eggs have been typically a preserve of the rich. Despite prices having come down considerably over the past few decades due to the advent to market of Chinese-produced caviar, today, a single kilo still fetches an average of £2500, with some varieties selling for as much as £4800. Having won plaudits for its sustainability credentials, this farm has focused on maintaining high levels of water quality and the efficient use of energy with no mention whatsoever of the welfare of the cultured animals themselves.

In the UK, there are only two known domestic providers of caviar. One is currently inactive and the other imports its produce from Germany and China. There are also a handful of online suppliers which source this delicacy from across Europe and Iran. Nowadays, over 50% of global caviar supplies come from China, the world’s largest caviar producer. While British farms historically imported adult sturgeon and bred them to extract their eggs, now they just sell the end product directly.

The biology and behaviour of sturgeon in the wild

The UK is home to two species of sturgeon, the Atlantic sturgeon (Acipenser oxyrinchus) and the European sturgeon (Acipenser sturio). However, overfishing and the construction of hydroelectric dams in key rivers decimated  the populations of these ancient species. Dams in particular prevented their upstream migration for spawning thereby reducing the populations’ ability to replenish. 

Sturgeon are sensitive to poor water quality and need well-oxygenated waters and good quality gravel in order to spawn.  After spawning, sturgeon fry swim back downstream and remain in brackish estuaries until maturity. Here they forage for crustaceans and molluscs using the barbels and electro-sensors on their delicate pointed snouts.

After global stocks of wild sturgeon started to plummet in the second half of the 20th century, attention turned to farming these animals. However, being kept in an indoor recirculating system or a barren concrete tank is a poor substitute for a fish that can live as long as a human and that has evolved the ability to travel thousands of miles and against the current in order  to spawn.

The egg extraction process

At Nacarii Caviar, fish are separated by sex when they reach four years of age. In order to do this, they are fished out of the water and placed on their backs in a ‘stretcher’ for up to 10 minutes while their gonads are inspected by ultrasound. The males are sacrificed for their fillets and the females are left to grow to adulthood so they can produce eggs to be sold as caviar. 

While sturgeon mature much faster in captivity than in the wild, it still takes around seven years for a female sturgeon to start producing eggs. By that point, she easily weighs over 30 kg and is up to 1.5 m long. As with most carnivorous fishes reared in aquaculture systems, she is fed an artificial diet of fishmeal fish oil, crustaceans and soybean which partly accounts for the high cost of the end product. 

After having been left to grow for a few more years, the females are scanned again to check for eggs. If she is gravid, she’ll have a long, thick needle stuck into her abdomen to sample her eggs. If repeated scans reveal no eggs, it is assumed that she’s either infertile or that her gonads weren’t sufficiently developed initially to detect that ‘she’ was actually a male. If her eggs meet the necessary ‘quality indicators’ in terms of preferred size, colour and texture, she will be killed using electricity in a bath.

Though gourmet websites typically describe the fish being ‘humanely dispatched’, the grim reality is that many farmers kill their animals with a simple blow to the head.

Alternatives to slaughtering for egg extraction: the no-kill method

One obstacle to the existence of a successful sturgeon farming sector in the UK is the lack of a market for the animal’s fillet. In light of this, the “no-kill” technique developed by German researcher Angela Köhler, of the Alfred Wegener Institute Helmholtz Center of Polar and Marine Research (AWI), is likely to be the least wasteful option. 

With the no-kill method, the fish’s life is spared. Though the publicly provided details are vague, this is apparently achieved through the administration of hormones to stimulate egg release. The eggs are then extracted by massaging the fish’s belly whilst they are on their back. This is touted as the most humane and sustainable option. However, the fish are still destined to live out their long lives in barren tanks and undergo repeated “harvesting”. KC Caviar in the north of England will employ this method when they restart production.

Farmed fish need more stimulating environments

In his groundbreaking book What A Fish Knows, bestselling author Jonathan Balcombe speculates that humans find it easier to identify with fellow mammals such as cows and pigs than with fishes. Perhaps that’s why agriculture is miles ahead of aquaculture in terms of animal welfare.

For example, land-based animal farming has long recognised the need for environmental enrichment with many farmers providing some sort of structures for caged animals to play with, increasing the likelihood they’ll forage, feed and grow faster. 

Environmental enrichment needs to be both species and life stage specific, so for example, in the case of sturgeon, softer bottom sediments with stones, gravel and vegetation, are likely to be more welfare friendly than barren concrete tanks that they are commonly housed in. Diversifying food sources and providing hideouts could encourage active foraging behaviour and reduce aggression between conspecifics which might lead to less incidents of fin damage such as those observed at Nacarii Caviar.

Back in Spain, to apparently entertain the fish and encourage exercise, Nacarii Caviar farm staff throw pelleted food to the stocked sturgeon. The fish anticipate feeding times and follow their handlers along the walls of their tanks. More often than not, such as when weather conditions are not ideal for farm workers to be moving around the facility, feed is dispensed using automatic feeders.

With the introduction of the no-kill method in caviar production meaning that the animals can live even longer in captivity, it is now more important than ever that producers take the welfare of these animals seriously and implement strategies for enriching their environment. One logical place to start would be by providing natural bottom sediments and hiding structures.