Triploid rainbow trout are named triploid because they possess three sets of chromosomes which render them sterile. The triploidy process involves the heating of eggs at 26 to 27 degrees C for 20 minutes at 20 minutes after fertilization.
Why is sterile trout desirable? Research biologists contend that sterilization is beneficial to prevent hybridization of native strains of rainbows and cutthroat trout. Also, since they do not spawn, all their growth potential goes to growing as opposed to producing eggs or milt. Many trout die as a result of the stress of spawning so we expect the triploid trout to live longer.
In addition they have ravenous appetites and one fisherman is quoted as saying that he found the entire glass bottle of Berkley power bait in the stomach of a Triploid caught in Utah. (I do not know if I believe that.) All the above factors are believed to lead to larger trout.
For you who are interested, you can learn more at Northwest.con or Utah Wildlife.