Triploid trout can and do perform similarly to diploid trout in certain situations. However, survivability may be cause for concern and mortality of triploids could be exaggerated under less than desirable conditions. If Utah discontinues the production of diploid trout and mandates all rainbow trout stocked be triploids, then reduced survival in general and even total year-class failure can be expected in some situations. More inconsistent survival of stocked trout will likely occur at many reservoirs that have had consistently good sport fisheries. In addition, variable environmental conditions associated with reservoir management in Utah may make setting standard stocking quotas extremely difficult.
The practice of stocking sterile or triploid trout in conjunction with native
fish programs is still a viable management option in some instances. Many
native trout waters in Utah are located at higher elevations and are relatively isolated from many stocked waters. Thus managers could continue to protect native species by careful selection of where triploid and diploid trout are scheduled for stocking.
Conversion from traditional stocking practices of utilizing only diploid trout
to stocking only triploid trout should proceed with caution, especially in waters with marginal habitat conditions. Changes to ‘triploid-only stocking’ could impact traditional sport fisheries and may require an unrealistic demand on hatchery resources. Blanket policies of “one size fits all” or “all rainbow trout stocked in Utah will be triploids” is not necessarily the best management strategy.
Managers should evaluate individual waters based on: 1) threats to native
species, 2) habitat conditions, 3) fishing pressure, and 4) spawning/reproduction potential and balance these considerations to best utilize both diploid and triploid trout to improve sport fisheries and better protect native fish. In some situations, native fish or sterile hybrids such as tiger trout (Salmo trutta X Salvelinus fontinalis) could be substituted in sport fish management when necessary; however, hatchery production must be improved to use these resources at a larger scale.
It should be noted that as of January 2009 the Utah Division of Wildlife
Resources has not discontinued the use of diploid rainbow trout and is in the
process of evaluating and changing current policy as it relates to triploid trout.