River Darter
  • Side view adult.
  • Side view adult.
  • Side view adult.
  • Top view adult.
  • Bottom view adult.
  • Head-on view adult.
  • Close-up flank.
  • Close-up head.
  • Close-up mouth and snout.
  • Close-up tail.
  • Close-up dorsal fin.
  • Close-up anal fin.
  • Close-up pectoral fin.
  • Close-up pelvic fin.
  • Close-up tail region: There are 19-24 scales around the caudal peduncle.
  • The sides show 8-11 blotches/bars and 48-60 lateral line scales; the 1st dorsal lobe has blotches on front and back.
  • Close-up mouth: The mouth is small and subterminal without obvious teeth, the snout is rounded and there is a dark bar below the eye.
  • Close-up dorsal fin: The 1st dorsal lobe has 10-12 spines and is dusky with pigment blotches anteriorly and posteriorly.
  • Close-up flank: The flank shows 8-11 irregular blotches in back and thin vertical bars in front as well as 65-71 lateral line scales.
  • Close-up belly: The scales on the belly and between the pelvic fins are enlarged and toothed.
  • Close-up anal fin of a breeder: Breeders are similar to non-breeders except that males show an enlarged anal fin.
DescriptionSimilar Species
Family
Perches (Percidae)
Body
Mouth and snout: Mouth slightly subterminal to terminal, horizontal to slightly oblique, minute teeth on jaws. No barbels. Body patterning, color, and scales: Back dark olive or brown with diffuse dark blotches or saddles. Sides lighter colored with 8-11 dark blotches, thick and irregular in back but grading to thin vertical bars in front. Belly white or cream. Second dorsal and caudal fins lightly speckled or barred, other fins lightly pigmented or clear. 48-60 ctenoid lateral scales. Body shape and size: Body fusiform to cylindrical and elongated; round to oval in cross section. Typically 50-65 mm (2-2.5 in) TL; maximum in Wisconsin about 80 mm (3.2 in).
Fins
Tail, dorsal and other fins: Square to slightly forked tail. Dorsal fin with 2 lobes, distinctly separate, the first with 10-12 (usually 10) spines and the second with 13-15 (usually 14) rays. Pelvic fins thoracic. Adipose fin absent. Anal fin with 2 spines and 11-12 (usually 11) rays.
Distinguishing Characteristics
The river darter can be distinguished by its small-to-moderate (not extending beyond the anterior of eye) terminal or subterminal mouth without obvious canine teeth, the presence of one or more enlarged and heavily toothed scales between the pelvic fins, plus usually a row of enlarged toothed scales along the midline in males and a partially naked belly in females. See also similar species information.
Breeding Adults
Males with minute tubercles on fins, head, & scales, anal fin enlarged (photos).
Juveniles
Similar to adults.
Hybrids
None known from Wisconsin.
Compare Similar Species
Snout
Darter, BlacksideRounded, not elongated
Darter, GiltRounded, not elongated
Darter, RiverRounded, not elongated
Darter, SlenderheadPointed, elongated
LogperchConical protuberance, somewhat elongated
Body Pattern
Darter, Blackside6-11 oval blotches along lateral line, stripe-like, blotches or saddles on back
Darter, Gilt5-8 thick squarish vertical bars or blotches extending on to back
Darter, River8-11 blotches, thick and irregular in back, grading to thin vertical ars in front
Darter, Slenderhead10-16 blotches or irregular vertical bars on sides, back
Logperch15-25 narrow vertical bars
1st Dorsal Fin Pigmentation
Darter, BlacksideSolid pigment on lower half, grading to dusky on outer third, thin light edge
Darter, GiltSolid pigment, orangish in life, except for thin clear/white edge
Darter, RiverDusky, with small dark blotch in front, larger dark blotch on posterior membranes
Darter, SlenderheadDark pigment on lower 1/2, then orange (in life), then dark band, then light edge
LogperchDusky lateral bands on light background
Lateral Line Scales
Darter, Blackside56-68
Darter, Gilt61-71
Darter, River48-60
Darter, Slenderhead65-71
Logperch71-79
Other Characteristics
Darter, Blackside~10 long gill rakers, 20-23 CP scales, 12-15 D1 spines
Darter, Gilt~11 long gill rakers, 24-29 CP scales, 11-12 D1 spines
Darter, River~9 short gill rakers, 19-24 CP scales, 10-12 D1 spines
Darter, Slenderhead~10 short gill rakers, 23-25 CP scales, 12-13 D1 spines
Logperch~12 short gill rakers, 24-37 CP scales, 13-15 D1 spines
Similarity Index
Darter, BlacksideVery similar
Darter, GiltVery similar
Darter, RiverN/A
Darter, SlenderheadVery similar
LogperchVery similar
Comments
Darter, BlacksideCP=caudal peduncle, D1=1st dorsal fin
Darter, GiltCP=caudal peduncle, D1=1st dorsal fin
Darter, RiverCP=caudal peduncle, D1=1st dorsal fin
Darter, SlenderheadCP=caudal peduncle, D1=1st dorsal fin
LogperchCP=caudal peduncle, D1=1st dorsal fin
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