How is fish roe harvested and made into fine caviar?

There are now two main methods in which the eggs of a fish are extracted from an individual fish and made into the popular caviar delicacy.

The Classic Harvesting Method

For centuries, the process to obtain caviar has been nearly the same. Despite advances in farming, fishing and production technology, the general step-by-step practice of harvesting fish roe has not changed, remaining basically the same practice that has been passed down from generation to generation.

With the decline of wild sturgeon populations, this traditional Russian and Iranian technique, has been put in a more controversial light. This is because the classic method requires that the sturgeon, or other fish being harvested for roe, is killed in order to harvest its eggs. 

  1. In modern fish farms and fisheries, the adult roe-carrying fish is slowly cooled in ice-cold waters to reduce their movement and render them unconscious before being brought to harvest.
  2. The entire fish is cleaned with purified water and the incision is made along the fish's belly.
  3. Most fish have two roe sacks. These are removed before the fish is fully dead, otherwise the body will release a chemical which will harm the eggs. The egg sacks are cleaned and the remainder of the fish is set aside to be harvested for meat.
  4. Each roe sack, or skein as they are called in salmon and trout, is screened on a sieve or other mesh screen to separate the eggs from the membrane.
  5. These green eggs are washed and filtered a second time, then drained and set aside to be weighed, salt-cured and graded.


The Humane Harvesting Method

Unlike the classic method of harvesting fish roe, there is a way to get caviar without killing the fish providing the roe. Known as "no-kill", or "cruelty" free caviar, this method usually uses hormone therapy combined with milking techniques and/or simple surgery to get stabilized eggs without harming the fish.

Due to the network of cells which stabilize a fish's egg, all unfertilized mature eggs are inedible as soon as they leave the mother and enter the water, and are impossible to collect after they have been fertilized. That is the reason that immature eggs are traditionally cut from the fish before they have a chance to be delivered. Most recently, marine biologists such as German Scientist Angela Köhler (accredited for introducing the fish-milking Köhler process to the caviar industry) have altered fish breeder reproduction techniques to create a process by which eggs can be delivered and used to make caviar without having to cut the mother at all.

  1. When an ovulating fish is nearly ready to lay their eggs, they are usually injected with a protein or hormone to separate the eggs from the membranous sack in the belly cavity, as would happen naturally right before delivering eggs.
  2. If necessary, the fish will either be cooled or sedated in some manner to prevent potential stress to the animal and damage to the product. 
  3. The fish is washed in purified water and the eggs are removed by one of two ways:
    1. C-Section method: A small incision is made on the female sturgeon's belly and their eggs are carefully scooped out. After all the roe has been removed the fish is sewn back up and bandaged. However, this method can leave the sturgeon vulnerable to infections, and can damage their reproductive organs if not done properly.
    2. Vivace method: Instead of an incision, this method utilizes a fish-milking technique know as striping, to massage the eggs out of the fish like a natural delivery. In order to make sure that the fish eggs keep their texture and do not turn into mush when harvested, they must be rinsed in a water-calcium solution immediately after being removed. This makes the green roe strong enough to withstand further handling, salting and curing.
  4. The green eggs are tested for firmness, then washed and filtered. After draining, the eggs are weighed, salt-cured and graded.


Although the classic method has more historical precedent and is still more widely used today than the humane method, no-kill caviar has been praised by conservationist for helping to increase the sustainability of certain fish, especially endangered sturgeon species. Since sturgeon take a decade before they're old enough to develop eggs and can also live for a century, it makes sense to try and keep these fish alive after extracting their roe. In addition to preventing the killing of a potentially endangered species, having the same female produce multiple harvests of roe can eventually cut down costs for aqua farms.

Despite the potential benefits of using the humane method, it still hasn't quite caught on yet. Most of the world's caviar is currently made by using the classic harvesting method to extract the raw material from its source. The additional cost of investing in the hormones, chemicals and equipment necessary to produce no-kill caviar has prevented it from being as affordable as classically harvested caviar. Also, just as traditional caviar may not be a good choice for those who deem it to be unethical, certain people, such as pregnant women, will not be able to eat caviar from humane sources because of the hormones and/or proteins used to extract the roe.




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