Tiger Trout
Tiger trout are sterile hybrids of the brown trout (Salmo trutta) and the brook trout (Salvelinus fontinalis). Their name is derived from the exaggerated vermiculations that evoke a mental image of tiger stripes. Due to brook trout having 84 chromosomes and the brown trout 80 this hybrid rarely occurs naturally in the wild, although instances have been reported for decades.
Hatcheries are able to produce good numbers of tigers by fertilizing brown trout eggs with brook trout milt. However, the survival rate of the eggs is typically low, rarely exceeding 25%, compared to the 85% typically achieved with brown trout.   Thanks to hybrid vigor, tiger trout reportedly grow much faster than either parentage.
Tiger’s markings are considerably different from their parents, and rather striking. The vermiculations of the male brook trout appear enlarged and twisted into a stripe-like pattern. Most also have a greenish cast, especially along the back. 
Highly piscivorous (fish-eating), tiger trout are stocked not only for their sporting qualities, but also as a means of controlling stunted populations of brook trout and rough fish, such as suckers.  Consequently, Utah Division of Wildlife Resources has been stocking them frequently, being sterile, they are able to control their population numbers also.
When fall water temperatures and day length perfectly align, brown trout are cued to begin their annual spawn. Providing the egg component, female brown trout are netted and her eggs are removed by gently stroking the fish’s belly in the direction of a vent, located just in front of the tail. Next, sperm from a male Trapper’s Lake brook trout is added to the pan along with a splash of water, to activate the fertilization process.
Tiger trout are sterile hybrids of male brook trout and female brown trout. While they rarely occur naturally in nature, they are stocked as a control measure for stunted brook trout and rough fish, such as suckers, in Colorado by Colorado Parks and Wildlife.  In addition to being used as a control measure, they offer fisherman an excellent sport fish opportunity.
 
Because of hybrid vigor and nature of the species, tiger trout are known for their quick growth rate as well as large overall size.  Tigers are fairly disease resistant, making them a valuable species with their resistance to whirling disease.  Again, because of their parent species, they are best targeted with minnow imitation lures and flies once they are big enough to switch over to a fish diet.
 
Their coloration and markings very greatly from brightly buttered color to extremely dull grey.  Overall, the vermiculations otherwise known as "worm shapes" on top of a brook trout are more pronounced that often look like a tiger pattern.  In addition to tiger striping you will also find larger uniformed colored spots.  While most trout show a mixture of multiple colors within their body, Tiger Trout will most often only have two major colors.
 
Because these fish are created within a laboratory setting and are more expensive to create, please consider catch and release of this species.
 
-Courtesy Alan Peak
 
Anglers salivating to knock this species off the proverbial bucket list will have additional opportunities in the near future as Colorado Parks and Wildlife plans to expand production by collecting trout eggs and sperm at additional lakes, other than North Delany (browns) and Trappers (brook trout). For those that simply cannot wait, a select group of waters near Cameron Pass were stocked with tiger trout in 2011, with additional stocking planned for in 2013 for mountain lakes within the Poudre and Big Thompson River drainages.

(Per Ben Swigle, Coloradoan 2013)