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Family Gasterosteidae STICKLEBACKS Members of this family are found in shallow water, both salt and fresh, throughout North America, Europe, Asia and Algeria, (Scott and Crossman 1973). One species, the brook stickleback, is BROOK STICKLEBACK Culaea inconstans (Kirtland) A small, laterally-compressed fish; head conical with a truncate lower jaw; unique dorsal fin composed of (average 5) short, isolated backswept spines with individual membranes followed by 9 soft dorsal rays united by one membrane; rounded caudal fin, anal fin with one spine anteriorly; pec- toral fins composed of one spine and one ray; body without scales although there are small plates by lateral line pores. Adults are dark green to black with light spots on sides. Spawning males often appear completely black. A small fish, adults are about two inches long. Range: The brook stickleback is found throughout north-central North America. Disjunct populations found in northeast New Mexico are considered native to that state (Koster 1957). Colorado populations are scattered throughout the South Platte drainage (Propst 1982), in parts of the Arkansas system (Miller 1983), and the Rio Grande (L. Zuckerman 1983). The presence of the species in areas where sport fisheries are absent led Propst (1982) to believe the brook stickleback is native to Colorado. The scattered popula- tions of the stickleback in other portions of Colorado where there are no sport fisheries would tend to support the thesis that sticklebacks are native. Since there are no fisheries near locations where several stickleback populations are found, chances that the species originated in Col- orado as a bait-bucket transfer are rather remote. Habitat: Brook sticklebacks inhabit cool, clear, slow flowing small streams and ponds with large amounts of filamentous algae and other aquatic plants. A pug- nacious fish, stickleback are generally found alone if in backwaters or in associa- tion with fathead minnows, creek chubs and plains killifish if inhabiting undercut found in Colorado. Another species, the threespine stickleback Gasterosteus aculeatus (Linnaeus) has been reported in Colorado. banks (Propst 1982). If streams contain- ing brook stickleback are channelized or dewatered, the species disappears (Trautman 1957). A carnivorous species, this fish eats a wide variety of aquatic invertebrates along with the eggs and larvae of other species (Scott and Crossman 1973). The following account of the spawning habitats of the brook stickleback was taken from Winn (1960). The species spawns from spring into summer halting when water tempera- tures exceed 66° F. Males move into shallow water and construct a nest about 3/4 inch in diameter of stems or grass. A series of females is driven into the nest through nips and nudges by the male. The females lay eggs after prodding by the male, and are then driven from the nest. Following fertilization the male guards eggs and fry until the young abandon the nest. Brook stickleback are not a very good bait fish. Even so, they are occasionally found in bait buckets. Due to its pug- nacious character and egg-eating habits the species' use as a bait fish is discour- aged in order to avoid accidental range expansion. For additional information regarding the brook stickleback see Winn, H.E. 1960. Biology of the Brook stickleback Eucalia inconstans (Kirtland). Am. Midland Nat. 63(2):424-438. ---- -? --?- i, 17 i r? L ri -1 I I __/ i r -- I • i • I 1 I Distribution by County of the brook stickleback. I I ?y 3 I - s-- - JI r 15 Colorado's Little Fish