Cannibalism happening in tanks across the region

A bigger trout digesting a smaller trout in a tank at a Union Springs classroom in 2015

It seems every year, we hear of reports of cannibalism in trout tanks across the region. Sometimes there is a suspicion that cannibalism is happening, as trout seem to be "disappearing" from the tank, and one or two trout are abnormally larger than the rest. But sometimes, students actually see a larger trout eating a smaller one in action, as they will spot a fish tail hanging from a trout's mouth. 

Trout, like many fish are cannibalistic and will likely eat smaller members of their own species. This is an example of natural selection, as some trout are better at adapting to their environment. 

When visiting schools, I always ask students for an update about what's going on in their tank, especially since they are spending a lot more time interacting with their trout aquarium than I am. One of the first things I usually hear about is the possible cannibalism happening. I often ask students why they think this is happening. Then I'll ask them which kind of trout has a greater chance of surviving in the wild, the small trout or the bigger trout that is able to eat the smaller trout?

A trout that has moved beyond small, dried up fish food and is able to capture live, moving fish in their environment indicates smarter, faster, more agile behaviors. Wouldn't a fish displaying these behaviors have a better chance of fighting off future predators like bigger fish, otters and birds of prey?

An angler in Strawberry Reservoir in Utah found a partially digested fish in the mouth of a cutthroat trout. Brett Prettyman/Trout Unlimited