Triploid

This extra set of chromosomes is often artificially induced by humans through techniques like thermal shock, pressure shock, or chemical treatments during the egg fertilisation process.

The main reason for doing this, in aquaculture,  is to ensure the fish are sterile and any that escape are unable to breed with wild populations.

Triploid fish often have slightly enhanced growth rates, especially since they do not use energy for reproductive development. This can make them more desirable for aquaculture, as they may reach market size faster.

There are disadvantages for triploids, however. Studies have shown that triploid fish are more likely to suffer from diseases or other health challenges,  including skeletal and heart deformities, cataracts and infections.

In Norway In April 2021, the Norwegian Food Safety Authority limited the release of triploid salmon to ongoing trials. All triploid salmon in these trials were due for slaughter by December 31, 2023. 

A study by the Institute of Marine Research (Havforskningsinstituttet) found a higher incidence of winter ulcers and mortality among triploid fish. They were also found to show inferior product quality and feed conversion rates.