Fish stocks have high natural productivity, but it is not unlimited. If more fish are caught than the natural surplus of the stock, the production potential for the future is reduced. To have a system of fishing rules in place is therefore in everybody's interest, to make sure fish stocks are shared fairly and are not depleted in the long run.
There are three types of fishing rules.
- Fishing effort limitations - restrict the size of the fleet that sets to sea and the amount of time it can spend fishing (see fishing effort).
- Catch limits - restrict the quantity of fish that can be taken from the sea before fishers need to stop fishing (see TACs and quotas).
- Technical measures - regulate how and where fishers can fish. They can, for example, be used to protect young fish (juveniles), encourage the use of more selective fishing gear or prevent serious damage to the marine environment (see technical measures).
Fisheries policy uses all three tools, separately or in combination. The multi-annual plans, put in place to manage specific fish stocks are often a mix of all three.