Meda fulgida

The following description is from Girard (1857), Miller and Hubbs (1960) and Minckley (1973). Adult spikedace are typically less than 70 mm in total length (TL), slim, and slightly compressed laterally. Scales are present only as small plates deeply embedded in the skin. The dorsal fin has a short base with usually seven rays, the first two being spinose, the anterior one being grooved to receive the second. The first spinous ray of the dorsal fin is stronger than the second, almost as long, and sharply pointed. Anal fins usually have 9 rays. Medial edges of the pelvic fins are adnate to the belly. The eyes and mouth are both relatively large and barbels are absent. Pharyngeal teeth are typically 1,4-4,1. The sides are silvery with vertically elongated black specks. The dorsum is olive-gray to brownish, usually mottled with darker pigmentation while the belly is white.

Breeding males have a golden or brassy sheen, especially on the head and at bases of fins. Gilbert and Scofield (1898) and Miller and Hubbs (1960) noted the presence of rose or reddish colors. Even in the nonbreeding season the sides have been described as appearing "...like burnished silver..." (Miller and Hubbs 1960). Both sexes have breeding tubercles, but they are better developed, and therefore more visible, in males. Abarca (1990) suggested the following method for distinguishing between sexes: for males the eye diameter is greater than the distance between the distal end of the pectoral fin (when folded back parallel with the long axis of the body) and the origin of the pelvic fins; for females the eye diameter is equal to or less than the distance between the distal end of the pectoral fin and origin of the pelvic fins.

Larvae have a nearly vertical mouth that makes them relatively easy to distinguish from other cyprinid larvae of the lower Colorado River Basin (Winn and Miller 1954).

The spikedace is a member of the tribe Plagopterini (Miller and Hubbs 1960). Other species of this tribe in Arizona are the woundfin (PLAGOPTERUS ARGENTISSIMUS), Little Colorado River spinedace (LEPIDOMEDA VITTATA), and Virgin River spinedace (LEPIDOMEDA MOLLISPINIS MOLLISPINIS). These fishes, plus the introduced carp (CYPRINUS CARPIO) and goldfish (CARASSIUS AURATUS), are the only cyprinid fishes in Arizona and New Mexico with fin rays modified as spines.

Characters that easily distinguish the spikedace from other Plagopterini in Arizona and New Mexico are the following: woundfin has a single barbel at each side of the upperjaw and an anal fin with 10 rather than 9 soft rays; Little Colorado River and Virgin River spinedace have visible scalation and the first spinose ray of the dorsal fin is weaker and obviously shorter than the second; carp and goldfish have long dorsal fins with more than 11 soft rays.

Habitat includes permanent, flowing, unpolluted water of low gradient streams having pool, riffle, run, and backwater areas; sand, gravel, and cobble substrates with low to moderate amounts of fine sediment and substrate embeddedness; abundant aquatic insects; natural hydrologic conditions, including recurrent flooding; few or no predatory or competitive non-native species present; a healthy riparian community; and moderate to high bank stability (USFWS, Federal Register, 8 March 1994; USFWS 1999). In larger rivers, spikedace often are found in the vicinity of tributary mouths. Adults favor slow to swift velocities (0-100 cm/sec) in shallow water (3-38 cm) with shear zones where rapid flow borders slower flow, areas of sheet flow at the upper ends of mid-channel sand/gravel bars, and eddies at downstream riffle edges. Juveniles favor slow to moderate flow (0-60 cm/sec) in shallow water (3-70 cm) with moderate amounts of instream cover; shallow stream margins and backwater areas, over silt, sand, or gravel bottoms, adjacent to pools. Periodic spates that scour and clean sands and gravels are essential to feeding and reproduction (Sublette et al. 1990). See Barber and Minckley (1966), Anderson (1978), Propst and Bestgen (1986), Propst et al. (1986), and Sublette et al. (1990) for further details. This species may partition habitat with red shiner in areas where the two species co-occur (Rinne 1991).

Spawning occurs over shallow (less than 15 cm deep), sand-gravel-bottomed riffles where water flow is moderate (Minckley 1973, Sublette et al. 1990). Eggs develop in sand or gravel at spawning site (Sublette et al. 1990). Stability of the substrate is likely important during times of egg deposition and hatching (Minckley 1981). Larvae occur in areas of slow to moderate flow (0-30 cm/sec) in shallow water (3-30 cm) with abundant instream cover.

Habitat utilization in the Cliff-Valley reach of the Gila River was studied by Propst et al. (1986). Juveniles (26-35 mm TL) were found to occupy an average depth of 16.1 cm and average current speed of 16.8 cm/s. Adults (>36 mm TL) in the same reach occupied an average depth of 19.3 cm and current of 49.1 cm/s. Spikedace occupied swifter waters in the warmer months of June to November than in the cooler months of December to May. Although habitat availability was not recorded, Propst et al. (1986) believed this to be a real shift. Sixty-percent of larval spikedace were captured over sand-dominated substrate, 18% over gravel, and 18% over cobble substrates. Juveniles were found over gravel substrates (46%), sand-dominated substrates (45%), and cobble substrates (9%). Adults were captured over gravel substrates (47%), cobble substrates (32%), and sand-dominated substrates (19%).

Rinne and Kroeger (1988) observed spikedace in Aravaipa Creek at an average depth of 20 cm and current speed of 35 cm/s over gravel and pebble substrates (3-64 mm diameter). Schools of 10 of more fish were found in deeper and slower water than solitary fish. Seasonal differences were documented in use of depths but not currents. Spikedace collected in December, February, and August occupied shallower depths than those collected in April, May, and September. Rinne and Kroeger stated these differences showed no discernible pattern and were probably related to availability.

The spikedace is associated with a native fish fauna that includes roundtail chub (Gila robusta), loach minnow (Tiaroga cobitis), speckled dace (Rhinichthys osculus), longfin dace (Agosia chrysogaster), Sonora sucker (Catostomus insignis), and desert sucker (Catostomus clarkii). Historically, it was also associated with the woundfin (Plagopterus argentissimus), bonytail (Gila elegans), squawfish (Ptychocheilus lucius), and razorback sucker (Xyrauchen texanus), all now extirpated from the Gila River basin.

Due to difficulties in tagging small fishes, movement patterns of spikedace adults are unquantified.

Minckley (1981) showed that populations of spikedace in Aravaipa Creek increased following years of relatively high flow.

Males evidently are not territorial but remain evenly spaced throughout a patrolled area. Females generally enter the area from downstream and are chased by males. The chase terminates when the female either strikes the bottom, or halts, in a group of males. Eggs are presumed to be spawned at this time (Barber et al. 1970, Minckley 1973).

Breeding color and tubercles may appear as early as December and last until August (Minckley 1981). Breeding may be triggered by a combination of temperature and stream discharge (Propst et al. 1986), as also documented for Rhinichthys osculus (John 1963). Gonads generally increase in size in February. Spawning first occurs in March when water temperatures reach approximately 19 C and proceeds until June (Minckley 1973, Anderson 1978), but mature ovaries have been noted in September (Minckley 1981). Propst et al. (1986) identified April as the peak breeding period and stated that spawning was completed by mid-May. Older females spawn earlier than younger females (Anderson 1978).

Number of eggs per female ranges from 80 to 300 or more depending on female size. Anderson (1978) examined a sample of 29 females from the Gila River, 10 km south of Cliff, New Mexico; these ranged in size from 38 to 70 mm TL, with 88 to 246 mature ova per female. Anderson (1978) computed the relationship between female body size and fecundity as follows: number of ova = -152.85 + 5.61 TL (r = 0.844). Ovum diameter at spawning is near 1.5 mm. Age II females spawn at least twice per season, but most reproductive effort is by age I females (Barber et al. 1970, Anderson 1978, Sublette et al. 1990).

Young first appear in April and May and reach 41 to 47 mm TL by November. Standard length (tip of snout to end of hypural plate) is related to total length by the following equation: SL = 0.85 TL - 0.12, r X r = 0.99, n = 100 (Marsh 1988). Total length averages 47 mm TL at the end of the first year, and 59 to 74 mm at the end of the second year. Sexual maturity occurs at about 40 mm in both sexes (Barber et al. 1970), and most become sexually mature in their second summer of life. Longevity typically is one to two years. Few live through their fourth summer and the largest individuals rarely exceed 70 mm (TL?) (Minckley 1973). Anderson (1978) reported an 81 mm TL female. Growth continues in the winter in Aravaipa Creek (Barber et al. 1970) but not in the cooler Gila River in New Mexico (Anderson 1978).