Blue Catfish
CatfishIctalurus furcatus · also called blue cat, hump-back blue
The largest catfish in North America, reaching well over a hundred pounds. It is distinguished from the channel catfish by counting the rays in the anal fin and by the shape of that fin's outer edge.
Quick facts
- Appearance
- Slate-blue to silvery-grey with no spots at any age, a deeply forked tail, and a straight-edged anal fin. A pronounced hump in front of the dorsal fin on large fish.
- Typical size
- 2–40 lb
- Waters
- river, reservoir
- Regulations
- Introduced outside its native range in several regions where it is now invasive, and some states encourage removal there while protecting it elsewhere. Rules differ sharply by state.
How to confirm it
- Anal fin edge is straight, like a comb, with 30 to 36 rays.
- No spots at any size.
- Deeply forked tail.
- Distinct hump in front of the dorsal on large fish.
What it is confused with
One check settles each of these.
The anal fin: straight-edged with 30+ rays means blue, rounded with under 30 means channel.
Why this matters beyond curiosity
- Look-alike species often carry different limits. Walleye and sauger, black and white crappie, pike and muskie, blue and channel catfish — each pair can have different sizes, seasons and daily limits in the same water.
- Check it before the fish goes in the livewell. Most of the tests on this site take seconds and are far easier on a fish you are still holding.
- If you cannot tell, release it. That is the answer that is never wrong, and it is the one a warden will not argue with.
- Regulations are set by your state or province and change annually. This site identifies fish; it does not tell you the rules. Check the current regulations for the water you are on.