https://www.pnas.org/doi/10.1073/pnas.1512955113This is about how they crossed female goldfish and male common carp to produce hybrids. After a couple generations of being diploids, they turned into tetraploids, and they use them to cross with another kind of carp to produce sterile triploid carp for commercial fish farming purposes.
However, tetraploid fish in and of themselves (without a thought to triploids and diploids) have great potential for value.