How carp are farmed and bred

Carp farming has a long history and most of the carp stocked into UK fisheries are produced in controlled conditions.

The farming process can be split into two basic phases. The first is the hatchery where the brood fish are spawned and the eggs and fry are produced, and the next phase is the on-growing process which is happens in ponds.

In this first of two articles I will look at the how the carp are spawned and the eggs produced.

Brood fish are generally four years old and have developed gonads which are ready to spawn. In the wild, this is governed by temperature. For farming, the process needs to be more timely and so a hormone is used to induce them to spawn.

This means that the whole process is more predictable and fish held in warm water all year round can be spawned at any time throughout the seasons.

1. Broodstock carp are selected on the basis of ripeness and health. Good female broodstock fish have a large egg mass and so appear fat. Once spawned, the fish recover their energy and rebuild their gonads. A female carp could potentially be spawned three times a year if kept warm and well fed.

2. The fish are given a series of injections with a hormone that starts the final gonad maturation process. After the final injection the carp will spawn the very next day.

3. Once the final maturation process has been completed the fish are removed from their holding facility.

4. If the series of injections has been successful then the eggs can be squeezed out of the female and collected. It is very important that no water touches the eggs at this point or they can't be fertilised. Note the towel to keep the water off the eggs.

5. The milt, or male sperm, can also be collected by gently squeezing the belly. Like the eggs it's important to ensure that no water goes in with the milt.

6. The milt and eggs are mixed together and fertilisation of the eggs begins.

7. The sperm enters the egg via a small hole called a micropile. Once a sperm has entered, the hole seals up stopping other sperm getting in.

8. A solution to improve the number of eggs fertilised is also added. The eggs are then stirred for about an hour and then rinsed to remove the stickiness.

9. Once the eggs have been treated to remove the stickiness they are placed in an incubation jar. This maintains a flow of clean water over the eggs to keep them healthy.

10. Once the sperm has entered the egg, the egg and sperm combine, forming the new carp. Within the first hour the egg cell starts its first division and a carp is being created.

11. The eggs gently roll inside the incubator and develop. They will hatch after about three days.