9550

• UCREFRP Catalog Number: 9550
• Author: Snyder, D. E. and R. T. Muth.
• Title: Catostomid Fish Larvae and Early Juveniles of the Upper Colorado River Basin - Morphological Descriptions, Comparisons, and Computer-interactive Key.
• USFW Year: 2004.
• USFW - Doc Type: Fort Collins, CO.
• Copyright Material: NO

Species Account - Catostomus discobolus

Fig. 49. Catostomus discobolus adult (@ Joseph R.
Tomelleri).

Adult Description: No conspicuous predorsal keel. Caudal
peduncle slender to deep, 3.2-10% SL, often correlated with
habitat. Mouth inferior and well back. Hard, truncate, cartila-
ginous ridges along inside of jaws, especially prominent on
lower jaw. Lips large with notches at outer comers, papillose
except on outer face of upper lip; lower lip with shallow cleft,
lobes broadly connected by 3 or more rows of papillae usually
concentric with the anterior margin of the lip. Fontanelle
typically closed. Pelvic axillary process absent or a simple
fold. Interradial membranes of caudal fin well pigmented.
Peritoneum black to dusky. TL usually 25-35 em, up to 40
em. (Also, Table 16.)

Reproduction: Non-guarding, open-substrate lithophil. May to
September, usually June and July, at 15-180C (sometimes also
in fall or winter in Lower Colorado River Basin based on
observations of ripe fish and collections of larvae). Water-
hardened eggs 3.3-3.5 mm diameter, demersal, initially adhesive.

Young: Later stage protolarvae and mesolarvae drift, predomin-
ately at night. Young typically occupy slow, shallow waters,
often <0.5 m, near shore and in backwaters; sometimes trapped
in cut-off pools or channels. Often associated with juveniles of
other species.

j

:-------. --~. ---.-. -'-
"
\
\

Fig. 50. Recent distribution of Catostomus discobolus
in Colorado River Basin.

Table 16. Selected juvenile and adult meristics for Catostomus discobo/us. P = principal rays; R = rudimentary rays; D =
dorsal; V = ventral. Scales are lateral series or line when complete. Four added to vertebral count for Weberian complex. Gill
rakers for exterior row of first arch, specimens> 70 mm SL. Mean or modal values underlined if known and noteworthy; rare
or questionable extremes in parentheses.

Character Original Literature Character Original
Dorsal Fin Rays - P: (9)10-11(12) 9-10-11-12 Dorsal Fin Rays - R: 2-1
Anal Fin Rays - P: 7 7(8) Anal Fin Rays - R: 2(3)
Caudal Fin Rays - P: (17) 18 Caudal Fin Rays - RD: (10)11-12
Pectoral Fin Rays: 14-11-16 Caudal Fin Rays - RV: 9-lQ(11)
Pelvic Fin Rays: 8-9-10 (7)8-2-10(11 ) Lateral Scales:
Vertebrae: 47-49 45-47-49-50 Gill Rakers:

Literature

(78-)86-115(-122)
28-35-44

Table 17. Size at apparent onset of selected developmental events for Catostomus discobo/us, as observed under low power
magnification. P = principal rays; R = rudimentary rays. Scales are lateral series. Rare or questionable extremes in parentheses.

Event or Onset or Formation Fin Rays First Formed Last Formed
Structure mmSL mmTL or Scales mmSL mmTL mmSL mmTL
Hatched: (8)9-10(11 ) (8)9-11 Dorsal - P: (11-)13(14) (12-)14(15) (14)15 (16)17-18
Eyes Pigmented: 9-10 or * (9)10 or * Anal - P: 14-15 16-17 (15-)17 (18-)20
Yolk Assimilated: (10-)12-14 (11)12-14(15) Caudal- P: 10-12(13) 11-12(13) (11)12-13(14) (12)13-14(15)
Finfold Absorbed: 21-22(23) 26-27(28) Caudal - R: 14 15 19-20 23-25
Pectoral Fin Buds: (8) or * (8) or * Pectoral: 14-15 16-17 16-18(19) 18-21 (23)
Pelvic Fin Buds: 14 (15)16 Pelvic: (15)16 18-19 19-20 23-25
* before hatching Scales: 28-34 (34)35-42 30-39 36-48

References: Andreasen and Barnes 1975, Baxter and Simon 1970, Baxter and Stone 1995, Beckman 1952, Behnke et a1. 1982,
Bezzerides and Bestgen 2002, Carlson et a1. 1979, Cope 1872, Douglas and Douglas 2000, Holden 1973, Hubbs and Hubbs 1947,
Hubbs et al. 1943, Jordan and Evennann 1896, Lee et a1. 1980, McAda 1977, Miller 1952, Minckley 1973, Prewitt 1977, Sigler and
Miller 1963, Smith 1966, Sublette et a1. 1990, Tyus et a1. 1982, Vanicek 1967, Wheeler 1997, Woodling 1985.

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