Slender Madtom
  • Side view adult.
  • Side view adult.
  • Side view adult.
  • Top view adult.
  • Bottom view adult.
  • Head-on view adult.
  • Close-up flank.
  • Close-up head.
  • Close-up mouth and snout.
  • Close-up tail. Tail of this specimen is missing a piece on the top lobe.
  • Close-up dorsal fin.
  • Close-up anal fin.
  • Close-up pectoral fin.
  • Close-up pelvic fin.
  • Notice that the adipose fin is continuous with the caudal fin with just a shallow notch between them.
  • The sides display a solid color without a dark lateral stripe; the edges of the dorsal, anal, and tail fins are dark; the body has a slender shape.
  • Close-up inside of mouth: Notice that there are no horn-like backward lateral extensions of the tooth patch on the roof of the mouth.
  • Close-up head: The upper and lower jaws are about equal in length.
  • Close-up pectoral spine: Notice that the pectoral spine has saw-like teeth.
  • Side view of a breeder: Breeders are similar to non-breeders; pregnant females are much deeper bodied than non-breeders or males.
  • Alternative side view.
DescriptionSimilar Species
Bullhead Catfishes (Ictaluridae)
Mouth and snout: Terminal or slightly subterminal, patches of numerous fine teeth on jaws. 8 obvious barbels (4 pairs; 2 pair on chin, 1 pair on side of upper jaw (near corner of mouth), 1 pair on top of snout). Body patterning, color, and scales: Solid color. Color dark brown, dark olive, or black; belly cream. Fins and barbels moderately to darkly pigmented (chin barbels often cream); dorsal, anal, and tail fins often with darker margins. No scales. Body shape and size: Body dorsal-ventrally flattened with a flattened head; in cross section approximately oval (with a long horizontal axis) to round with a flattened ventral surface. Typically 75-115 mm (3-4.5 in) TL; maximum in Wisconsin about 125 mm (5 in).
Tail, dorsal and other fins: Rounded tail. Single dorsal with 1 stout spine and 6-7 rays, attached by membrane. Pelvic fins abdominal. Adipose fin present, attached to caudal by a membrane with a shallow notch between them. Anal fin with 18-21 rays (including rudimentary rays).
Distinguishing Characteristics
The slender madtom can be distinguished by its adipose fin, which is attached to the back and caudal fin. See also similar species information.
Breeding Adults
Similar to non-breeders.
Similar to adults.
None reported from Wisconsin.
Compare Similar Species
Tooth Patch on Roof of Mouth
Madtom, SlenderNo horn-like backward lateral extensions
Madtom, TadpoleNo horn-like backward lateral extensions
StonecatHorn-like backward lateral extensions present
Color Pattern
Madtom, SlenderNo dark lateral stripe; dorsal, anal, tail fins usually with darker edges
Madtom, TadpoleOften with pencil-thin dark lateral stripe; dorsal, anal, tail fins without darker edges
StonecatNo dark lateral stripe; dorsal, anal, tail fins with lighter edges or sometimes uniformly pigmented
Pectoral Spine
Madtom, SlenderProminent saw-like teeth on posterior margin
Madtom, TadpoleNo or a few very fine teeth
StonecatNo or a few very fine teeth
Jaw Lengths
Madtom, SlenderAbout equal or upper jaw very slightly longer
Madtom, TadpoleAbout equal or upper jaw very slightly longer
StonecatUpper jaw clearly longer than lower (i.e., subterminal mouth)
Body Depth/Std Length
Madtom, Slender<22%
Madtom, Tadpole>22%
Similarity Index
Madtom, SlenderN/A
Madtom, TadpoleVery similar
StonecatVery similar