Transcript:

Today on Animal Fact Files we’re discussing rainbow trout. These fish are also called redband trout, and, depending on where and how they live, they're sometimes known by another name. Those that spend part of their lives in the ocean are also known as steelhead trout. While most rainbow trout migrate, not all individuals make their way out to saltwater. Fish that live in saltwater and then migrate to freshwater for spawning are known as anadromous fish. Not all rainbow trout are anadromous, but it's difficult to tell just by their behavior. The offspring of fully freshwater rainbow trout parents can end up living in saltwater, and anadromous parents can have offspring that only live in freshwater. It's not fully understood why this happens!

In either case, these fish prefer cool waters and tend to spawn in fall or winter. They live from the open ocean to freshwater lakes and rivers. Their natural range extends across the western coast of North America reaching as far east as the Rocky Mountains, however, they've been introduced throughout the United States and other countries where they're sometimes considered a pest due to their breeding with local trout species. In many places, rainbow trout can't handle the heat of summer temperatures so they must be restocked annually in order to maintain their populations.

Unlike salmon, another anadromous fish, rainbow trout are iteroparous. This means rainbow trout can produce offspring multiple times over the course of their life as long as they can avoid predators. Aside from humans who fish rainbow trout for sport and food, these fish are predated by otters, bears, and wading birds like herons. Salmon, a trout relative, die after spawning, but rainbow trout can return to the same breeding grounds multiple times throughout their lives. Those that live exclusively in freshwater move upstream to spawn, and those that live in the ocean move to freshwater swimming up waterfalls by jumping more than ten feet (3 m) in the air. 

The female digs out a pit at the bottom of the water column in rocky or sandy substrate. Once completed, she rests in the nest and a male enters. They release their gametes into the nest at the same time. There can be hundreds to thousands of eggs per spawning event! Afterwards, the female covers the eggs with substrate and then the process begins all over again. It takes about three weeks for the eggs to hatch and some of the juveniles spend more than a year in freshwater before heading to the ocean while others may take to saltwater within just a few months! Again, it's not known why this occurs. 

It takes two to three years for rainbow trout to reach reproductive maturity and females take longer than males. They get their common name from their colorful scales, often spotting a red line along their sides. Their backs are speckled. In size, these fish reach about two feet long (61 cm) though outstanding individuals can almost double this length. Typically the largest growing rainbow trout are the steelhead variety. No matter where they live, these fish enjoy meals of both aquatic plants, invertebrates, and fish. When they're young, they eat smaller meals like zooplankton and bits of algae. As they get older, they eat larger meals sometimes even eating the unfortunate mouse which has fallen in the water. The oldest known rainbow trout was just over a decade old!

For more facts on rainbow trout, check out the links below. Give a thumbs up if you learned something new today. Thank you to our Patrons SpikeSpiegel93, Dad, and everyone else for their support of this channel! And thank you for watching Animal Fact Files!