Cottus cognatus
Slimy Sculpin

Slimy Sculpin

Flora, fauna, earth, and sky...
The natural history of the northwoods



  • Cottus, an old name for a European fish, the Miller's Thumb
  • cognatus, from the Latin, "kindred"; a reference to it's close relation to the European Cottus gobio
  • Common Name
  • Other common names include: Cockatouch, Cottus Big Fin, Northern Miller`s Thumb, Northern Sculpin, Sculpin, Slimy Muddler


  • Kingdom Animalia
    • Phylum Chordata, animals with a spinal chord
    • Subphylum Vertebrata, animals with a backbone
      • Superclass Osteichthyes, bony fishes
      • Class Actinopterygii, ray-finned and spiny rayed fishes
      • Subclass Neopterygii
      • Infraclass Teleostei
        • Superorder Acanthopterygii
        • Order Scorpaeniformes, scorpion fishes and sculpins
        • Suborder Cottoidei, sculpins
          • Family Cottidae, bullheads, scaleless sculpins, sculpins
            • Genus Cottus, the Miller's Thumbs, freshwater sculpins


  • A little, odd-looking fish of small streams
  • Length rarely exceeds 4"
  • Weight
  • Color
    • head, back, and sides olive brown with dark mottling
    • lower region of head and belly lighter to whitish
    • When motionless in one place for long periods of time, its coloration so perfectly blends into the surroundings that it is difficult to observe.
  • Body
    • anterior flattened dorso-ventrally
    • posterior body and caudal peduncle compressed laterally
    • two lobed, narrowly connected dorsal fins
      • frontal dorsal fin has 7 to 9 soft spines
      • second lobe has l6 to l8 rays
    • anal fin of 11- 13 rays
    • pelvic fins thoracic with a single spine and 3 pelvic rays
    • pectoral fin of 13-14 rays
    • Scales absent and lateral line incomplete, ending under second dorsal fin
  • Head
    • head flattened dorso-ventrally
    • terminal mouth with numerous teeth in narrow bands on the upper and lower jaws
  • Lifespan at least 5 years.


  • Unmistakable as a sculpin
  • Distinguished from the nearly identical Mottled Sculpin (Cottus bairdi) by generally having only 3 soft rays in each pelvic fin, where the Mottled Sculpin has 4.


  • Northern North America, from Alaska to Virginia; also northeast Asia.
  • Shallows of Lake Superior and the streams of the North Shore.


  • Lives on stream bottom. Movements are darter-like in their rapidity and often resemble hopping.
  • Activity mostly nocturnal.


  • Primarily aquatic insect larva and other invertebrates.
  • Sculpins have long been accused of trout egg and fry predation and even for direct competition for benthic invertebrates. Most of the trout eggs consumed are probably loose eggs that were not buried in the redd. Little evidence is available which shows sculpin limit trout numbers. It has even been speculated that sculpin predation on predaceous stoneflies may increase the numbers of drifting herbivorous insects for trout and reduce stonefly predation on trout eggs and young.




  • Spawns in late April and May. A nest cavity is cleaned by the male; eggs are deposited by the female in clusters on the undersides of stones. The male guards the nest 3 to 4 weeks, until the fry leave.



Boreal border

Last updated on 15 October 1999