Fish certified as organic is always farmed fish. Fish captured in the wild cannot be certified as being organic.
Organic fish farming is subject to many sustainability requirements. The organic legislation also contains requirements concerning the origin of juveniles, animal welfare, the fish food used, the slaughter techniques, and the aquatic systems.
Closed recirculating systems are prohibited (except for hatcheries and nurseries). In a closed recirculating system, there is no natural flow of water but water is pumped around.
In practice, this limitation means that the Netherlands is not particularly suitable for organic fish farming. (In the Netherlands, fish is farmed almost exclusively in closed systems.)
Article 15 of Regulation (EC) No. 834/2007: basic legislation (PDF)contains more information about the basic requirements. Organic fish comes from systems in which you can control the conditions, such as aquaculture systems. From page 27 (chapter 2b) onwards of Regulation (EC) No. 889/2008: provisions governing implementation (PDF) you’ll find the requirements for fish farming. Dutch fish farmers who are interested in organic certification after reading the legislation can contact the Agriculture team at Skal.