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When you look at pictures of steelhead and rainbow trout next to each other, they look nearly identical. They are, in fact, the same species: Oncorhynchus mykiss. But just as greyhounds and pit bulls are the same species with several divergent traits, steelhead and rainbow trout have many key differences between them. Let’s look at them next to each other: Between steelhead and rainbow trout, what’s the difference?
Both rainbow trout and steelhead start their life cycles in similar ways: they hatch in streams, lakes, and rivers. However, steelhead trout get a little stir crazy. They’re drawn to the sea from day one, and they spend the majority of their life cycles there before returning to a river or stream later in life.
Rainbow trout, meanwhile, are homebodies. They’re content to stay in freshwater environments, often in the same lake or river where they hatched, for their whole lives.
Contrary to what their names might suggest, steelhead trout are actually the more colorful of the two! After they migrate to the sea and return to freshwater lakes and streams, their coloring explodes from steely blue and green to a bright rainbow. Steelhead are also known for a distinct silvery sheen on their scales as well as a bright red stripe along the sides.
Rainbow trout’s colors are more modest, in shades of blue, green, and yellow. Their reddish stripe is more subdued.
A fish never stops growing, but some environments encourage growth more than others. When steelhead migrate to the ocean, their habitat suddenly becomes much bigger, and they can reach lengths of up to 45 inches. (The vast majority, however, are not that big.) But because rainbow trout spend the entirety of their lives in smaller freshwater environments, they generally don’t grow larger than 16 inches long. Rainbow trout can and do grow to similar sizes as the average steelhead fish, but that growth takes longer.
As fish grow, their scales see some wear and tear and can develop scarring. Because steelhead trout explode in size and coloring when they migrate to the sea and back, they’re more likely to have visible scars. Plus, saltwater environments are harder on scales than freshwater.
Rainbow trout, on the other hand, grow more slowly. They’ll still have scarring from growth and age, but the scars will be subtler.
On your next fishing trip, pay close attention to your catches and compare and contrast them. Steelhead and rainbow trout are often found alongside one another, but there are a few key differences to watch out for. Compare your steelhead and rainbow trout—what’s the difference? Now that you know what to look for, you’ll identify them more easily.