Physiology
• A rainbow trout has a long, skinny body and can come in a variety of colours from brown and black to olive and blue-green. No matter the colour, the rainbow trout always has a reddish stripe length-wise down both sides of its body.
• The fish’s underbelly is white and tiny black spots cover its back, sides and fins.
• The rainbow trout actually has seven fins in total: a pair of pectoral fins, a pair of pelvic fins, an anal fin, a dorsal fin and an adipose fin. To distinguish wild rainbow trout from the hatchery kind, fish hatched and raised in captivity and then released into the wild, oftentimes the adipose fin will be clipped in the hatchery variety.
• The fish has sharp teeth on the roof of its mouth but has no lower teeth at all.
Key Distinguishing Markings
• Rainbow coloration varies widely. The same batch of rainbows grown at two different hatcheries can have noticeably different colour intensities and patterns.
• For the most part, rainbow trouts have a greenish silver back and a silver sides with a faint red band that travel the length of the lateral line.
• They are heavily spotted along the sides and top to include the dorsal and tail fins.
Size
• The average size range of rainbow trout is 10-13 inches with some individuals reach 20+ inches.
Habitat
• Rainbow trout are carnivores that won’t eat any vegetation growing in the water. Insects, leeches, small fish, crayfish and mussels are just a few delicious treats a rainbow trout likes to munch on.
• This fish likes to live in cool freshwater but some of them migrate into saltwater and become steelhead trout. Steelheads are the same as rainbow trout except in saltwater, the fish gets bigger, eats larger prey and has to return to its birthplace to spawn, much like a salmon. However, the freshwater rainbow trout does not have to migrate back to its birthplace to lay its eggs.
• To lay her eggs, a female rainbow trout must dig a nest in the gravel at the bottom of the body of water. To build this nest, called a red, the female turns her body to the side and flaps her tail, creating a depression in the gravel. She then lays up to thousands of eggs. As she is doing this, one or more male rainbow trout fertilize the eggs with something called milt.
Food Preference
• Like other trout species, rainbows are opportunistic feeders and consume a large variety of aquatic and terrestrial insects and macro invertebrates.
• When stocked in large lakes, rainbow trout, unlike brook and brown trout, can grow very quickly strictly on a diet of lake plankton.
Source: www.dnr.state.md.us www.canadiangeographic.ca
