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KEY TO GENERA PERCIDAE

1. Free edges of preopercle with strong teeth; mouth large, the maxilla extending
backward to middle of eye:.............................................................…............. 2
 
1. Free edges of preopercle with weak teeth or none; mouth small, the maxilla not
reaching backward to middle of eye; body depth contained less than 7 times in
standard length; body normally scaled except for a naked strip on midline of
belly in some species:...........................................................................…........ 5

2. Canine teeth present; space between pelvic fins equal to length of pelvic base;
pseudobranchiae well developed: (Stizostedion) .............................................. 3

2. Canine teeth absent' space between pelvic fins less than length of pelvic base;
pseudobranchiae not well developed: ................Yellow Perch - Perca flavescens
 

3. Irregular rows of round, black dots on dorsal fins; rays of soft dorsan fin about
17: .......................................................…....... Sauger - Stizostedion canadense

3. Dorsal fins with obscure dusky mottlings; end of spinous dorsal with a large
black blotch; rays of soft dorsal 19 to 22: ....................................................... 4

4. Body in life with brassy yellow mottlings, never bluish; lower fins clear
yellowish: ...................................Yellow Walleye - Stizostedion vitreum vitreum

4. Body in life grayish blue, without brassy yellow mottlings; lower fins bluish
white: .......................................... Blue Walleye - Stizostedion vitreum glaucum

 
5. Midline of belly with a row of enlarge, specialized scales; one specialized
scale between pelvic fins; pelvic fins separated by a space more than 3/4 the
width of the pelvic fin base; anal fin usually as large as the second dorsal
fin: (Percina) ................................................................................…............ 6

5. Midline of belly scaleless or variously scaled with normal scales, but lacking
a row of enlarge, specialized scales; no specialized scale between the pelvic
fins; pelvic fins closer together, separated by a space less than 3/4 the width of
the pelvic fin base; anal fin usually much smaller than the second dorsal fin:
(Etheostoma) ...............................................................................…........... 8

6. Snout conical, pig-like; more than 80 scales in lateral line; numerous bars on
sides; up to 6 inches in length: ............................ Logperch - Percina caprodes

6. Snout not conical; scales less than 80 in lateral line: .................................. 7

7. Gill covers well divided, meeting in an acute angle over isthmus: ................
.......................................................…... Blackside Darter - Percina maculata

7. Gill covers moderately joined across isthmus, resulting in an angle of almost
90 degrees between membranes; length of snout about equal to anterior-
posterior diameter of eye: ........... Slenderhead Darter - Percina phoxocephala

 
8. Deep groove separates tip of upper jaw from snout: ................................ 9

8. Tip of upper jaw connected to snout by a frenum, which may be narrow or
broad: ............................................................................…...................... 10

9. Two anal spines; snout extends beyond upper lip: Greenside Darter -
.....................................................................…........ Etheostoma blennioides

9. One weak, flexible, anal spine; usually 11 or less rays in soft dorsal fin:
.....................................................…...... Johnny Darter - Etheostoma nigrum

 
10. Gill covers broadly connected across isthmus, usually resulting in an obtuse
angle between branchiostegal membranes when in the closed position: .......... 11

10. Gill covers free from isthmus to moderately connected, resulting in an acute
angle between branchiostegal membranes: ......................................…......... 13

11. Mouth terminal; head long and narrow; lateral line incomplete, pored
scales ending beneath soft dorsal; tail round: ....................... Fantail Darter -
..............................................................................……. Etheostoma flabellare

11. Mouth subterminal; snout rounded, head triangular; lateral line complete;
tail slightly forked or squarish: ........................................…......................... 12

12. Cheeks and opercles scaled; body with 10 or more vertical bands; dorsal
spines usually 10 or 11: ............................ Banded Darter - Etheostoma zonale

12. Cheeks and opercles scaleless; body with 4 prominent saddles across back;
dorsal spines usually 12 or 13: ...........Variegated Darter - Etheostoma variatum

13. Lateral line incomplete with posterior 10 to 12 scales lacking pores; no visible scales on cheeks; rays in soft dorsal fin 11 or more; spines in anterior dorsal fin usually 10 or 11; belly behind pelvic covered with imbricated scales; body covered with bars and blotches: ..............................................................................Rainbow Darter - Etheostoma caeruleum

13. Lateral line complete; snout sharply pointed; dorsal profile from nape to
tip of upper lip nearly straight: ........... Spotted Darter - Etheostoma maculatum

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