Here's why:
* Freeze Tolerance: Some trout species, like brook trout, have evolved a remarkable ability to survive freezing temperatures. This is because they can produce a type of "antifreeze" protein that lowers the freezing point of their bodily fluids.
* Ice Crystal Formation: When water freezes, ice crystals form. These crystals can damage cells, which is why freezing is generally deadly. However, trout can limit the formation of ice crystals by producing antifreeze proteins.
* Metabolic Slowdown: When a trout freezes, its metabolic rate slows down dramatically. This allows them to conserve energy and survive until warmer temperatures return.
* Not All Trout Are Created Equal: While some trout species are quite freeze-tolerant, others are not. For example, rainbow trout and brown trout are less able to withstand freezing temperatures.
Important Note: Even freeze-tolerant trout have limits. If the water temperature drops below their critical threshold, they will likely die. The specific freezing point varies between species and even within individual fish.
So, in summary, while some trout species can survive being frozen, it's not a guarantee. Several factors play a role, including species, water temperature, and the duration of the freezing event.