Triploid oysters have three sets of chromosomes which causes them to be infertile. This is a common technique in agriculture and is not genetic modification. All seedless fruit and bananas are triploid as are most trout. In all other respects they are identical to normal (‘diploid’) oysters.

Although there are theoretical advantages for growth rate (since they need less energy for reproduction), in practice most people find they grow about the same as diploids. The difference is in the summer, or Autumn in cooler locations, when the triploids should retain a better meat quality by not being ‘milky’ which some consumers and chefs find unattractive.