Photo by Chad Thomas, Texas State University-San Marcos
Lake Petén, Guatemala (Günther 1866).
Etymology/Derivation of Scientific Name
Doro, meaning “lanceolate”; soma, meaning “body”, in reference to the body shape of the young; petenense, for Lake Petén, Guatemala, the type locality (Scharpf 2005).
Meletta petenensis Günther 1866:603.
Signalosa atchafalayae Evermann and Kendall 1898:127.
Dorosoma petense Cook 1959:67.
Maximum size: 203 mm (7.99 in) TL (Lambou 1965).
Coloration: Dorsal region blue-green with yellow hue; lateral region silvery-white with black shoulder spot, ventral region silvery-white. Fins are yellow except for dorsal fin.
Counts: 40-48 lateral scales; 24-28 anal soft fin rays; 11-14 dorsal soft fin rays; 12-17 pectoral soft fin rays, 7-8 pelvic soft fin rays, 16-17 ventral scutes anterior to pelvic fin, and 9-11 postpelvic scutes (Miller 1963; Hubbs et al. 1991; Ross 2001).
Body shape: Deep body, laterally compressed.
Mouth position: Terminal mouth; level with eye (Hubbs et al. 1991).
Morphology: Adipose eyelid; axillary scale at base of pelvic fins; last ray of dorsal fin greatly elongated; ventral scales form a serrated edge. Numerous pyloric caeca (Goldstein and Simon 1999).
Distribution (Native and Introduced)
U.S. distribution: Native to Mississippi River drainage and gulf slope drainages from Florida to Central America (Hubbs et al. 1991).
Texas distribution: Eastern half of the state (Hubbs et al. 1991). Warren et al. (2000) listed the following drainage units for distribution of threadfin shad in the state: Red River (from the mouth upstream to and including the Kiamichi River), Sabine Lake (including minor coastal drainages west to Galveston Bay), Galveston Bay (including minor coastal drainages west to mouth of Brazos River), Brazos River, Colorado River, San Antonio Bay (including minor coastal drainages west of mouth of Colorado River to mouth of Nueces River), Nueces River.
Abundance/Conservation status (Federal, State, Non-governmental organizations)
Currently stable in the southern United States (Warren et al. 2000).
Macrohabitat: Ponds, lakes, reservoirs, large rivers, and estuaries (Burgess 1980).
Mesohabitat: Generally pelagic midwater dwellers; prefer substrate of sand, mud, and organic debris (Wallus et al. 1990). Species often associated with flowing water (Burgess 1980), and moves in large schools (Wallus et al. 1990). In Texas, a preference is shown for brackish water with salinities of 10-20 ppt (Carlander 1969). Northern distribution limited by low tolerance of cold temperatures, 7-14°C (44.6-57.2°F) (Hubbs 1951; Burgess 1980). In laboratory experiments, Griffith (1978) found that feeding activity decreased at a water temperature of 10°C (50°F); fish were unresponsive to movements or vibrations when held at 6-7°C (42.8-44.6°F); fish did not survive when water temperature dropped below 5°C (41°F).
Spawning season: April through September; spawning reported to occur when temperatures are 14.4-27.2°C (57.9-81.0°F) (Carlander 1969; Wallus 1990).
Spawning location: In open waters, over plants or other objects (Miller 1963); spawn in aggregates under brush and floating logs, the eggs adhering to the brush (Carlander 1969; Burgess 1980; Wallus et al.1990).
Reproductive strategy: Nonguarders; open substratum spawners; phytophils - plant material nesters that have adhesive eggs and free embryos that hang on plants by cement glands (Wallus et al. 1990; Simon 1999). Threadfin shad school along the shoreline, with small groups of 1-2 females and 3-15 males breaking away and moving toward shore; the groups swim erratically near surface, then move quickly toward a log, vegetation or other submerged object while releasing eggs and milt (Lambou 1965; Wallus et al. 1990).
Fecundity: Fecundity reported to range from 800-21,000 eggs (Wallus et al. 1990). A 102 mm female may have 6,700-12,400 eggs (Carlander 1969). Females of 100-140 mm SL carry 5,292-17,339 eggs (Kilambi and Baglin 1969). Mature ova range from 0.74 – 0.94 mm in diameter immediately prior to spawning; fecundity 900-21,000 eggs, this dependent on size of female (Johnson 1971). Fertilized eggs have a gelatinous covering; measure 0.75-1.20 mm in diameter; are spherical; demersal; adhesive to slightly adhesive; and light yellow, or opaque to creamy yellow; hatching occurs in 3 days at 26.7 °C (Wallus et al. 1990). Large die-offs reported after spawning (Berry et al 1959); however, a large number of females and males survived to reproduce again (Johnson 1971).
Age at maturation: Possibly age 0, most by age 1 (age class 1; Berry et al. 1959; Miller 1963; Carlander 1969; Burgess 1980).
Migration: After introduction into California in 1955, this species moved north to Yaquina Bay, or via marine migration (Burgess 1980).
Longevity: Up to age 2, in Florida (Berry et al. 1959) and age 4, in Arizona (Johnson 1970). Females tend to live longer (Parsons and Kimsey 1954).
Food habits: Planktivore (Carlander 1969; Burgess 1980); trophic subclass: filter feeder; trophic mode: pump filtration (Goldstein and Simon 1999). Diet includes phytoplankton such as blue-green bacteria, diatoms, and green algae; dipteran larvae; water mites; invertebrate eggs; and fish larvae (Haskell 1959; Miller 1967; Baker and Schmitz 1971; Goldstein and Simon 1999). Baker and Schmitz (1971) noted that threadfin shad feed more in the water column than does the similar species D. cepedianum (gizzard shad), thus ingesting less organic detritus.
Growth and Population structure: Length (TL) up to 130 mm (5.12 in) at age 0 (Carlander 1969). Females tend to reach larger sizes than males (Parsons and Kimsey 1954).
Phylogeny and morphologically similar fishes
Similar to D. cepedianum (gizzard shad), which has a subterminal mouth, 59-67 lateral line scales, a longer anal fin (29-35 rays), and17-19 sharp scutes before the pelvic fins; caudal fin and back of D. petenense are more yellowish than in D. cepedianum (Miller and Robison 2004). Characteristics which differentiate D. petenense and D. cepedianum larvae: in fish ranging from 3-5 mm TL, the eye is pigmented in D. petenense, but is not in D. cepedianum; in fish ranging from 6-20 mm TL, D. petenense has 40-46 total myomeres, while D. cepedianum has 46-54 total myomeres; D. petenense specimens >22 mm TL have 17-27 anal fin rays, while D. cepedianum specimens >22 mm TL have 29-35 anal fin rays (Santucci and Heidinger 1986). Often found in swifter flowing waters (e.g. bases of spillways) than D. cepedianum (Burgess 1980). Can hybridize with D. cepedianum (Minckley and Krumholz 1960). D. cepedianum is superficially similar to Hiodon alosoides (goldeye), Alosa chrysochloris (skipjack herring), and Brevoortia patronus (Gulf menhaden) but differs in having an elongate last dorsal ray and median predorsal area naked and not crossed by scales (Boschung and Mayden 2004).
Protozoa: Crytobia sp. (Hoffman 1967).
Commercial or Environmental Importance
Widely introduced as a forage fish in reservoirs (Hubbs et al. 1991).
Baker, C.D. and E.H. Schmitz. 1971. Food habits of adult gizzard and threadfin shad in two Ozark reservoirs, pp. 3-11. In: Reservoir fisheries and limnology. G. E. Hall, ed, Spec. Publ., no8, American Fisheries Society, Washington D.C.
Berry, F.H., M.T. Huish, and H. Moody. 1959. Spawning mortality of the threadfin shad, Dorosoma petenense (Günther), in Florida. Copeia 1959(3):192.
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