Anyone care to share any info about them? I know they’re bred to get larger than your average fish, but other than that, I’m clueless.
It is not uncommon for plants and animals (including humans) to have more than the normal complement of chromosomes. This leads to differing expression levels of proteins and can create major difference in phenotype (the expressed characteristics of the creature), often deleterious and frequently causing infertility. Selective breeding has led to many muliploid food crops with desirable characteristics. Beyond that, I don’t know anything about triploid fish.
Here is a quote from the Wikipedia article on Brown Trout:
Farming of brown trout has included the production of infertile triploid fish by increasing the water temperature just after fertilisation of eggs, or more reliably by a process known as pressure shocking. Triploids are favoured by anglers because they grow faster and larger than diploid trout. Proponents of the stocking of triploids argue that, because they are infertile, they can be introduced into an environment that contains wild brown trout without the negative effects of cross-breeding. However, it is possible that stocking triploids may damage wild stocks in other ways. Triploids certainly compete with diploid fish for food, space and other resources. They could also be more aggressive than diploid fish and they may disturb spawning behaviour.
Triploids are generally infertile because the odd number of chromosomes makes it essentially impossible to get correct segregation during meiosis.
Many seedless fruits are the result of triploid plants.