Culaea inconstans
Brook Stickleback

Brook Stickleback

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



  • Culaea, a name coined just for this fish
  • inconstans, from the Latin, "variable"
  • Common name from the row of distinct spines on its back and from its preferred habitat
  • Other common names include: Black Stickleback, Common Stickleback, Five-spined Stickleback, Pinfish, Six-spined Stickleback, Variable Stickleback


  • 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 Gasterosteiformes
        • Suborder Gasterosteoidei
          • Family Gasterosteidae, the sticklebacks, consisting of 6 species in 5 genera in North America
            • Genus Culaea, the brook sticklebacks


  • A fascinating little fish of clear streams.
  • Length 2" to 3"
  • Weight
  • Coloration
    • olive green in color on the back and sides
    • white or yellow spots and dark wavy lines scattered over the sides
  • Body
    • deep-bodied, compressed
    • scaleless
    • 2-7 (usually 5) unconnected spines, followed by dorsal fin of 9-ll rays.
    • anal fin with a single spine and 9-l0 rays
    • pelvic fin with heavy spine and a single ray
    • complete lateral line with 30-36 small, bony plates along its length
  • Head
    • large, with large eyes
    • small mouth with swollen lips
    • lower jaw projects beyond upper jaw
  • Lifespan to three years.


  • Unmistakable as a stickleback.
  • Distinguished from the other northern stickleback, Newfoundland Stickleback (Pungitius pungitius), by having 5 (rather than 9) stickles on its back.


  • Northwest Territories east to Nova Scotia, south to Iowa.


  • Streams and some natural lakes.
  • Prefers streams with moderate currents over sand and gravel bottoms with clean to slightly turbid water.


  • Principally aquatic insects
  • Serves as forage for numerous game fish.



  • Provides many hours of fascinating entertainment for behavioral ichthyologists.


  • Nest building by males begins in the spring at water temperatures of 59º to 66º F. A rounded nest is built from organic debris, filamentous algae, and other materials. The nests are attached to a stem of vegetation by a whitish cement secreted by the male.
  • Male aggressively seeks a female that is gravid. The female enters the nest opening and is continuously prodded by the male until eggs are deposited. Immediately after leaving the nest the female is chased away by the male. The male then enters the nest and fertilizes the eggs.
  • Eggs are incubated by the male, vigorously fanning a current of water through the nest. Eggs hatch in 7-ll days, depending upon water temperature.
  • Male continues to guard nest after the eggs hatch, retrieving fry that stray by catching them in his mouth, one at a time, and spitting them back into the nest. After several days, young escape so fast the male is unable to retrieve them, and he either abandons the paternal duty or consumes his own offspring.


  • Stickleback behavior patterns are quite elaborate and have been studied intensively for many years.
  • Make interesting aquarium fish, but their aggressive behavior makes it difficult to keep other small fish.


Boreal border

Last updated on 17 October 1999