Picture by Chad Thomas, Texas State University-San Marcos
Chihuahua River and a tributary a few miles long, Mexico (Girard 1856).
Etymology/Derivation of Scientific Name
Campo – curved and stoma – mouth, referring to U-shaped mouth; ornate – referring to ornamental coloration of breeding males (Scharpf 2005).
Campostoma ornatum Girard 1856:176; Burr (1976).
Campostoma ornatum pricei Minckley 1973:141-142; McNatt 1974:275-276.
Maximum size: 114 mm (4.50 in) SL (Burr 1976).
Coloration: Burr (1976) noted an extreme variability in coloration both ontogenetically and among adults; most adults have mottled coloration; juveniles generally lack mottling but frequently have a dark mid-lateral stripe extending from snout to caudal peduncle and terminating in a small basicaudal spot; when mottling is developed in juveniles it is usually dorsal (within and above mid-lateral stripe); during non-breeding season, fins in both sexes are usually transparent but sometimes a black band may appear on the dorsal fin several months before the breeding season and continue through the season. Girard (1856) described coloration: upper regions purplish-black; lower regions golden-brown and yellow, with black spots distributed over the flanks; black patch at the base of all fins, otherwise the fins are orange or yellowish-brown. Burr (1976) described coloration of preserved breeding males: dorsal and anal fins often with a velvet-black medial band; pectoral and pelvic fins with black pigment heavily concentrated on the distal edges, becoming less intense proximally; black caudal spot lengthens transversely, often appearing as dark vertical band of pigment. In life, breeding male with distal half of dorsal fin milky white, basally fin is orange, and medially fin is velvet-black; anal fin similar to dorsal fin but with less black; caudal fin mostly milky white, with black and orange confined to the basal one-fourth; edge of shoulder girdle blackened (Burr 1976). In breeding females, a black band develops only on the dorsal fin (Burr 1976).
Counts: Pharyngeal teeth 0,4-4,0 (sometimes 1,4-4,1; Blair et al. 1957); 8 dorsal fin soft rays; 8 pelvic fin soft rays; 19 (18-20) caudal fin soft rays; 7 (rarely 8) anal fin soft rays; 16-18 pectoral fin soft rays; 14-20 moderately long, well separated gill rakers (Burr 1976). Burr (1976) listed the following counts for this species in the Rio Grande: 72 (65-78) lateral line scales; 55 (52-60) scales around body; 33 (30-37) predorsal scales; 28 (26-30) caudal peduncle scales; sum of lateral line and scales around body 127 (119-135); 28 (26-30) caudal peduncle scales.
Mouth position: Subterminal.
Body shape: Terete and stout.
Morphology: Cartilaginous ridge of lower jaw prominent and separated by a definite groove from lower lip (Hubbs et al. 1991). Breeding females with small tubercles on snout and above eye (Burr 1976). Intestine long, loops only partially around air bladder (Burr 1976).
Distribution (Native and Introduced)
U.S. distribution: Texas and Arizona (Miller 1972; Williams et al. 1989; Scharpf 2005); species found in Rucker Canyon and Leslie Creek, AZ (McNatt 1974; Burr 1976). Endemic around the Sierra Tarahumara and east to the Big Bend area (United States and Mexico; Contreras-Balderas 1974).
Texas distribution: Species occurs primarily in Mexico and ranges into Texas in Rio Grande tributaries in Brewster and Presidio counties (Big Bend region; Hubbs 1940; Hubbs 1954; Hubbs et al. 1991).
Abundance/Conservation status (Federal, State, Non-government organizations)
Listed as Threatened by the Texas Parks and Wildlife Department. Edwards et al. (2002) reported that their collections of Mexican stonerollers in the Rio Conchos basin and middle Rio Grande, Mexico and U.S.A. supported Threatened status for the species. Listed as Threatened in Texas by Hubbs et al. (1991). Watch List status by the Texas Organization for Endangered Species (1988). Endangered in Arizona (U.S. Fish and Wildlife Service 1994). Williams et al. (1989) listed Special Concern status due to present or threatened destruction, modification, or curtailment of habitat or range, and other natural or manmade factors affecting continued existence. Listed as Threatened (Miller 1972). Endangered in Mexico (CONABIO 1997); Endangered status in Mexico may refer only to local populations as the species, in general, is widespread and regionally abundant in the country (Miller et al. 2005; Scharpf 2005). Hubbs and Wauer (1973) suggested that Mexican stonerollers in Tornillo Creek, Texas may be stressed by the presence of an introduced species, the plains killifish (Fundulus zebrinus). Prior to the introduction of plains killifish (first collected from Big Bend area in 1954), Mexican stonerollers were the most abundant fish in Tornillo Creek, Texas (Hubbs and Wauer 1973). Hubbs and Wauer (1973) indicated relative abundance of this species ranged from 0-17% in Tornillo Creek, Texas; occurring in only 5 of the 11 samples taken during the period from 1967-1970.
Macrohabitat: Creeks and rivers (Burr 1976; Hubbs et al. 1977). In Texas, found in clear tributaries in the Big Bend region, but not in adjacent streams (Hubbs 1957).
Mesohabitat: Collected in riffles, chutes, and pools from warm, clear to slightly turbid water over substrate consisting primarily of sand, pebbles, gravel, rock, and bedrock; rarely collected over mud; species most often found in shallow water; apparent preference for headwaters; largest collections taken from gravel runs or gravel-bottom pools; vegetation may or may not be present (Burr 1976; Burr 1980). Prefers gravel or rocky bottoms in clear, cool water (Contreras-Balderas 1974). McNatt (1974) found species to be abundant in pools of Rucker Canyon, Arizona, especially the deepest pools.
Spawning season: Winter and spring, in Tornillo Creek, Texas; young and breeding adults were present in January and half-grown young in May and June (Hubbs and Wauer 1973). Burr (1976) reported presence of males nearing full tuberculation in October collections from Texas; in Mexico, nuptial males and gravid females were present in collections from February – June.
Spawning habitat: Tributary creek habitats (Hubbs and Wauer 1973; Edwards et al. 2002).
Spawning Behavior: Pit-builders (Johnston 1999).
Fecundity: No information at this time.
Age at maturation: Burr (1976) examined nuptial males ranging in size from 55-105 mm (2.10-4.13 in) SL.
Migration: No information at this time.
Growth and Population structure: Males attain a greater length than females (Burr 1976). In small pools in Rucker Canyon, Arizona, McNatt (1974) reported at least three age-classes (possibly four) present.
Longevity: No information at this time.
Food habits: Herbivorous, bottom feeder (Contreras-Balderas 1974). Burr (1976) reported that cursory examination of intestinal contents suggest diet very similar to that of the central stoneroller (C. anomalum), consisting mainly of diatoms, bacteria and algae.
Phylogeny and morphologically similar fishes
Campostoma ornatum is a highly variable species displaying numerous presumably primitive features for the genus (Burr 1976; Burr 1980). Closest relative is the central stoneroller (Campostoma anomalum; Burr 1980). C. ornatum has more than 65 lateral line scales and the lower jaw length is greater than the eye length, while C. anomalum has fewer than 60 lateral line scales and the lower jaw length is less than the eye length (Hubbs et al. 1991). Burr (1976) listed major features in which C. ornatum diverges from C. anomalum as: development of smaller scales; loss of tubercles on the nape; development of head tubercles on the female; and more reduced body size. C. ornatum is differentiated from other species of Campostoma by many morphological and biochemical characteristics (Buth and Burr 1978; Burr 1980). C. ornatum does not occur in sympatry with any other Campostoma species (Blum et al. 2008).
Individuals from the Rio Trujillo (Mexico) were found to be heavily diseased with a monogenetic fluke, and large nematode worms were entwined throughout the intestines of adults (Burr 1976).
Commercial or Environmental Importance
McNatt (1974) reported predation on this species by the rainbow trout, Oncorhynchus mykiss.
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