Production of all-female triploid rainbow trout

Triploid rainbow trout were produced by heat shock treatment of eggs soon after fertilization with either normal sperm or sperm from masculinised females. The proportion of triploid fry, as judged from red blood cell nuclear volume, varied between 75% and 100% in three experiments using different batches of eggs from an autumn-spawning strain of trout while a single batch of eggs from a winter-spawning strain yielded 50% triploids.

A microscopic examination of the gonads was made on 5-month-old fish weighing between 1 and 3 g. In female controls the ovaries were packed with oocytes while those from female triploids, although showing the typical lamellar structure of an ovary, contained no oocytes, thus indicating that female triploids are sterile. The testes from triploid males appeared to be developing normally.

The use of masculinized females combined with heat shock treatment of eggs to produce triploids, allowed the production of sterile all-female triploids. This should have considerable potential for aquaculture.