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How to Identify a Blue Catfish

The blue catfish (Ictalurus furcatus) is one of North America's biggest freshwater fish species, according to the National Audubon Society Field Guide to Fishes. The blue catfish inhabits the Mississippi River system from as far east as West Virginia to as far west as South Dakota, with its range extending southward to the Gulf Coast. Frequently mistaken for the very similar channel catfish, especially when they are immature, the blue catfish possesses certain characteristics that lead to correct identification.

Instructions

- 1
  Observe the colors of the blue catfish's body. The blue catfish has a white belly, but it has a bluish to slate gray tint on both its head and back, with the sides being lighter shades of these colors.
- 2
  Measure the size of the blue catfish. This fish averages between 18 and 24 inches, but much larger specimens exist; some blue catfish grow over 5 feet long. State records over 100 lbs. are common. For example, the Alabama state record for a blue catfish is 111 lbs. Nevertheless, most blue catfish will be in the range of 10 lbs., or even less.
- 3
  Examine the deeply forked tail of the blue catfish. This feature earns the blue catfish the nickname of the fork-tailed cat. On the opposite end of the fish, you should find white chin barbels, small appendages about the mouth that the blue catfish uses to feel for potential food in the water.
- 4
  Look at the jaw of the blue catfish. In most instances, the upper jaw projects beyond the lower jaw. There should also be a slightly raised hump just behind the head of the blue catfish on its back, between the head and the beginning of the upper (dorsal) fin.
- 5
  Inspect the lower rear (anal) fin of the blue catfish. The edges are straight on this catfish, as opposed to the rounded edge of the anal fin on a channel catfish. The small segments that together compose the anal fin on a blue catfish, called rays, number between 30 and 36 on this species. Channel catfish will have no more than 29 of these rays.

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