I had heard that the California Department of Fish and game had been raising triploid fish in recent years to avoid planting trout that are going to breed with native and threatened species of trout, and it appears the triploid tale is in fact true.
Carrie Wilson, a marine environmental scientist with the California Department of Fish and Wildlife, cleared the question up in her latest Q&A column today.
"Yes! These vivacious, catchable, sterilized rainbow trout are produced by California Department of Fish and Wildlife (CDFW) fish hatcheries," she noted.
For those who aren't familiar with triploids, they have an extra set of chromosomes that result in sterile fish, so they're "more ecologically sound option for recreational fishing in many waters across the state."
Additionally, anglers will like the fact that Wilson notes these fish often grow larger than fertile diploids.
Wilson added that this is a result of new legislation this year that requires the CDFW to sterilize nearly all fish planted for recreational purposes.
"This sterilization practice has been in place for decades and requires no manipulation of the cell genomes - no genes are modified or transferred in this process," she noted. "The carefully applied pressure during fertilization simply encourages the retention of an extra set of chromosomes normally in the egg but later discarded. Polyploidy (more than two sets of chromosomes) is common in the animal kingdom."
Interested in reading more about trout plants. Be sure to read our piece on how trout plants work.