GLACIER
Fishes of Glacier National Park Montana
Conservation Bulletin No. 22 		NPS Logo

KEY TO THE FISHES OF GLACIER NATIONAL PARK

The following descriptive key and the figures of the fishes of Glacier National Park will enable the layman, sportsman, and naturalist to identify the various fishes which they may take. Since the description of any group of animals as complex as the fishes is difficult to put into terms familiar to the layman, the footnotes and figure 1 should be consulted frequently. This key, like most zoological keys, has the statements arranged so that the user must consider alternative characters. One group of characters is given under a designation as "1a" and the contrasting character under "1b." In using the key to trace a fish down to its correct name, for example, the Rocky Mountain whitefish, proceed as follows: If 1a is correct, do not proceed to the alternative 1b, but go to the next number directly below 1a, on the same page, which is 2a. Since 2a is correct proceed to 3a and since 3a fits the whitefish, then go to the next number below, on the same page, which is 4a. But since the characters given under 4a do not fit the rocky mountain whitefish then proceed to the alternative 4b, which corresponds. Again 5a does not fit so turn to 5b which does. Since 6a is the next number below 5b, and the characteristics under 6a correspond with the specimen at hand, the fish is identified because the name, Prosopium williamsoni, occurs at the end of the paragraph.

FIGURE 1.—Outline drawing of Prosopium williamsoni, Rocky Mountain whitefish, to show anatomical characters and methods of measuring certain distances on fishes. Ac P—accessory pelvic scale; Ad—adipose fin; An F—anal fin; B DO—base of dorsal fin; By—branchiostegal rays; Cau F—caudal fin; D—dentary or lower jaw; D E—diameter of eye; Do F—dorsal fin; Le Cau Pe— length of caudal peduncle; Le H—length of head; Le Me—length of mouth; Le Sn—length of snout; Oc—Occiput; Op—opercular bone which forms part of the operculum; Pec F—pectoral fin; P F—pelvic fin; P mx—premaxillary; Pr—preopercular bone; Sc Ab Lat—showing how and where to count the number of scales above the lateral line; Sc Be Lat—showing how and where to count the number of scales below the lateral line; Sc Lat—showing where and how to count the number of scales in or scale rows crossing the lateral line; S mx—supplemental maxillary bone; St Le—standard length. (click on image for a PDF version)

1a. Two dorsal fins present, the second may be very small as in the case of an adipose fin, which lacks typical fin rays, or large when composed of normal fin rays.

2a. The second or posterior dorsal is an adipose fin, without rays, located behind the dorsal fin, over the caudal peduncle; no spines in any of the fins; scales cycloid and smooth; more than 55 oblique rows of scales crossing the lateral line.

3a. Fewer than 105 oblique scale rows on the side of the body from head to base of caudal fin rays; teeth weak in mouth on jaws.

4a. Dorsal fin with 20 to 245 rays; dorsal fin long and high, its base longer than the head; scales in about 90 to 100 oblique rows on side of body; pyloric caeca about 15 to 20. (Family Thymallidae).

5Throughout this report the number of soft rays in the dorsal and anal fins are counted as follows: The first one or two rudimentary rays, closely joined to the first complete ray, are omitted. The last two rays, sometimes branching from a common base, are counted as one ray.

Grayling. (fig. 13) Thymallus montanus Milner, p. 26, No. 11.

4b. Dorsal fin not long and high, of 10 to 15 rays, its base shorter than the length of the head; pyloric caeca more than 25. (Family Coregonidae).

5a. Scales on side of body in about 58 to 65 oblique rows, and about 8 scales above and 6 scales below the lateral line; back brownish; snout broad and very blunt; two flaps of skin between the nostrils.

Brown-backed whitefish. (fig. 11) Prosopium coulteri (Eigenmann and Eigenmann), p. 24, No. 9.

5b. Scales on side of body in 74 to 95 oblique rows; back more grayish brown; snout not definitely blunt.

6a. One flap of skin between the pair of nasal openings on each side of head; mouth small, the maxillary not reaching below eye; the supplemental maxillary bone5 narrow and sharply elliptical, more than 3 times as long as deep; gill rakers7 about 20 or fewer on the first arch; greatest depth of body 4 to 5 times in the length.

5Throughout this report the number of soft rays in the dorsal and anal fins are counted as follows: The first one or two rudimentary rays, closely joined to the first complete ray, are omitted. The last two rays, sometimes branching from a common base, are counted as one ray.

7All rudiments are counted.

Rocky Mountain whitefish. (figs. 9 and 10) Prosopium williamsoni Girard, p. 23, No. 8.

6b. Two flaps of skin between the nostrils; mouth larger, the maxillary reaching past front of eye, the supplemental maxillary6 bone ovate, nearly twice as long as deep; gill rakers7 about 27 to 29 on the first arch; greatest depth of body 3 to 4 times in its length.

6The supplemental maxillary bone is situated at the dorsal and posterior corner of the maxillary bone.

7All rudiments are counted.

Great Lakes whitefish. (fig. 12) Coregonus clupeaformis (Mitchill), p. 25, No. 10.

3b. More than 115 oblique rows of scales on the side of the body from head to base of caudal fin rays; teeth strong and sharp.

7a. Anal fin elongate of 13 to 175 rays (rarely 12); gill rakers rather long 11 to 24+20 to 268, usually totaling 31 to 507 on the first gill arch; anal and dorsal fins seldom with black spots; oblique scale rows 125 to 145 (usually about 130), and 19 to 24 scales above and 19 to 23 scales below the lateral line; young with rather large round black spots above the lateral line; sides red at spawning.

5Throughout this report the number of soft rays in the dorsal and anal fins are counted as follows: The first one or two rudimentary rays, closely joined to the first complete ray, are omitted. The last two rays, sometimes branching from a common base, are counted as one ray.

7All rudiments are counted.

8The gill-raker formula indicates the number of rakers on the upper half of the arch plus the number on the lower half.

Little redfish. Silver trout. Landlocked red salmon. (fig. 8) Oncorhynchus nerka (Walbaum), p. 22, No. 7.

7b. Anal fin short, of 9 to 12 (rarely 13) rays; gill rakers rather short 20 or fewer on first gill arch; dorsal fin usually with numerous black spots.

8a. Species with dark spots on a tighter background of color; less than 190 oblique scale rows crossing the lateral line; vomer flat, its toothed surface plane, teeth on shaft of the vomer in alternating rows or in one zigzag row, those on the shaft placed directly on the surface of the bone, not on a free crest.

9a. Red dash on dentary (between lower jaw bone and isthmus) evident in life; maxillary on adults extending behind eye; length of mouth contained 1.6 to 2.25 times in the head length; hyoid teeth (those located behind the patch of teeth on the tip of the tongue) usually present but few and scattered; vertebrae9 58 to 62 (usually about 60); dorsal rays 9 to 11 (usually 10 or 11); anal rays 9 to 11.

9The total number of vertebrae are counted from the upturned tip of the hypural plate to the head.

10a. Black spots large and scattered, most numerous posteriorly, those on anterior part of the body widely separated, the spots are usually absent on belly and sometimes to the lateral tine; scales above and below the lateral line 32 to 42 (usually 35 to 38); scales in the lateral line 156 to 190 (usually about 170); gill rakers 6 to 9+9 to 13 or totaling 15 to 22.

Montana black-spotted trout. Cutthroat trout. Native trout. (fig. 2) Salmo clarkii lewisi (Girard), p. 15, No. 1.

10b. Black spots very numerous and covering the body, a few occurring even on the belly; the spots are about as close together posteriorly as anteriorly; scales above the lateral line 35 or fewer; scales below the lateral line 35 or fewer; scales in the lateral line 120 to 180 (usually fewer than 160).

Coastal cutthroat trout. (fig. 3) Salmo clarkii clarkii Richardson, p. 18, No. 2.

9b. No red dash of color on dentary evident in life; dorsal rays 10 to 13 (usually 11 or 12); hyoid teeth always absent; vertebrae 59 to 65 (rarely 59 or 60, usually 63);9 color on sides reddish, the lateral band usually but slightly interrupted by faint parr marks on adults; gill rakers 7 to 9+9 to 13;8 length of mouth contained 2.0 to 2.5 times in the head length of adults and seldom extending behind eye; scales in 130 to 160 (usually about 135) oblique rows on side of body; 23 to 32 scales above and 20 to 30 scales below the lateral line; body profusely covered with black spots.

8The gill-raker formula indicates the number of rakers on the upper half of the arch plus the number on the lower half.

9The total number of vertebrae are counted from the upturned tip of the hypural plate to the head.

Rainbow trout. (fig. 4) Salmo gairdnerii Richardson p. 19, No. 3.

8b. Species with light spots (white or light gray, sometimes yellowish) on a darker background of color; often with red spots on the sides; over 190 scale rows crossing the lateral line; vomer with the shaft depressed and without teeth, but the head of the bone bears teeth.

11a. Vomer with a raised crest, projecting backward a little from the head of the bone, this crest armed with strong teeth; species gray-spotted, but without red spots; fins slightly bright (white) edged; 185 to 205 oblique scale rows on side of body; head about 4-1/2 times in length of body; the greatest depth of body about 4 in its length; diameter of eye about 4-1/2 times in the length of the head.

Lake trout. (fig. 7) Cristivomer namaycush (Walbaum), p. 21, No. 6.

11b. Vomer without a raised crest which extends backward, head of bone toothed; species red-spotted in life, the lower fins with bright silvery edgings.

12a. Back unspotted, instead it is strongly mottled with olive and black, the blotches connect with each other causing the mottled appearance; dorsal and caudal finely mottled; body robust or stout, the head heavy, scales in about 230 oblique rows along the side of the body.

Eastern brook trout. (fig. 6) Salvelinus fontinalis (Mitchill), p. 21, No. 5.

12b. Back not mottled, but with the light spots like those on the sides of the body, only smaller and paler; body less robust or stout, the head larger, about 3-2/3 in the standard length; scales in about 240 rows along the side of the body.

Dolly varden trout. Bull trout. Western Charr. (fig. 5) Salvelinus malma spectabilis (Girard), p. 19, No. 4.

2b. The second or posterior dorsal is not an adipose fin, but it is a normal fin composed of normal soft rays.

13a. No spines in any of the fins, all of the rays soft; anterior dorsal short, of 12 or 13 rays; second dorsal long, about three-fifths the length of the body with 70 to 75 rays; the anal long, about two-fifths the length of the body, with about 65 rays; pelvic fins located under the bases of the pectoral fins; body and head covered with very small embedded scales; tip of chin with barbel. (Family Gadidae).

Ling. Burbot. (fig. 24) Lota lota maculosa (Le Sueur), p. 35, No. 21.

13b. Spines are present in the first or anterior dorsal fin; pelvic fins with 1 spine, and 3 or 4 soft rays; body and head naked, no scales present, although the head may be profusely covered with prickles; first dorsal fin with VI to VIII10 spines; second dorsal with 16 to 19 soft rays; anal without spines, of 10 to 14 soft rays; lateral line incomplete or complete (if extending to base of caudal fin). (Family Cottidae).

10Roman numerals indicate spines and arabic numerals soft rays.

14a. Teeth on vomer and palatines; preopercle with a stout spine, its length not over half the diameter of eye, two or three small, short spines below, directed downward; lateral line incomplete ending under soft dorsal; sides without stiff prickles, usually but slightly roughened.

Blob. Bullhead. Sculpin. (fig. 25) Cottus panctulatus (Gill), p. 35, No. 22.

14b. Teeth on vomer, none on palatines; preopercle with an upturned curved spine, very large, about as long as eye, hooked backward and upward, giving a buffalolike appearance, below which are 2 or 3 smaller spines hooked downward; lateral line complete; sides with stiff prickles, head sometimes with prickles on the dorsal side.

Prickly sculpin (fig. 26). Cottus ricei Nelson, p. 37, No. 23.

1b. A single dorsal fin of soft rays only; the pelvic fins without spines, located ventrally, behind the pectoral fins on the abdomen, usually near the middle of body.

15a. Jaws, tongue, palatines, vomer, with teeth; origin of the dorsal fin in the posterior third of the body, tail fin not included; dorsal fin of 15 or 16 rays;5 anal of 14 or 15 rays; 122 to 125 rows of scales on side of body from head to base of caudal fin; jaws with large canine teeth; head about 2.9 to 3.6 in standard length; greatest depth of body is contained about 5 to 7 times in the Standard length; color of body darker with light spots. (Family Esocidae.)

5Throughout this report the number of soft rays in the dorsal and anal fins are counted as follows: The first one or two rudimentary rays, closely joined to the first complete ray, are omitted. The last two rays, sometimes branching from a common base, are counted as one ray.

Common pike. Pickerel (fig. 23). Esox lucius Linnaeus, p. 34, No. 20.

15b. Jaws, tongue, palatines, and vomer without teeth; origin of dorsal fin in middle third of the body (tail fin excluded) but it may continue into the posterior third; branchiostegals 3; gill membranes united to the isthmus.

16a. Mouth usually directed downward, excessively protractile and suckerlike with papillous lips; pharyngeal teeth in11 one row, comblike and numbering more than 10 on one side (bone). (Family Catostomidae.)

11The pharyngeal bones which bear the pharyngeal teeth are located behind the last gill arch and at the beginning of the oesophagus. These are best removed through the last gill cleft.

17a. Oblique scale rows fewer than 85 on the side of the body.

18a. Dorsal rays 12 to 15 (rarely 12)5; 12 to 17 scales above the lateral line; 65 to 80 (rarely more than 80) oblique rows of scales on side of body, and 8 to 10 scales below the lateral line; peritoneum white to dusky, the color not showing through the body wall in the young; caudal peduncle very slender in the young.

Columbia River coarse scaled sucker (figs. 14 and 15). Catostomus macrocheilus Girard, p. 27, No. 12.

18b. Dorsal rays 11 or 12; 63 to 70 oblique scale rows on side of body; 9 to 11 scales above the lateral line; and 8 or 9 scales below lateral line; peritoneum dusky, seldom whitish or silvery, the color sometimes showing through the body wall in the young; caudal peduncle robust.

Common sucker. White sucker (fig. 17). Catostomus commersonii (Lacepede), p. 30, No. 14.

17b. Oblique scale rows 98 to 115 on the side of the body; 18 to 21 scales above and 15 to 18 below the lateral line; dorsal rays 9 to 11 (rarely 11); peritoneum dusky, seldom whitish; caudal peduncle moderately slender.

Long-nosed sucker (fig. 16). Catostomus catostomus griseus Girard, p. 29, No. 13.

16b. Mouth not especially directed downward, nor excessively protractile; if inferior in position non-protractile; the lips are never papillous and not suckerlike; pharyngeal teeth in one or two rows and fewer than 8 on one bone, and never arranged like the teeth in a comb. (Family Cyprinidae.)

19a. Premaxillary not protractile, a broad frenum present, which binds it to the projecting snout; mouth inferior; barbel present on posterior edge of the maxillary; teeth usually 1: 4—4 : 1;12 dorsal rays 8 (rarely 9); scales in about 62 to 75 oblique rows.

12In Cyprinidae, the main row of teeth on each pharyngeal bone contains 4 or 5 teeth (seldom more or less); inside of this main row is a so-called "lesser row," which may contain 1 or 2 teeth or none, in the latter case being designated 0 in the formula, as, for example, "teeth 2: 4—4: 0," which means 4 teeth in each main (outer) row, and 2 teeth in one lesser row of one side and 0 teeth in the other lesser (inner) row of other side.

Long-nosed dace, Black nosed dace (fig. 20). Rhinichthys cataractae dulcis (Girard), p. 32, No. 17.

19b. Premaxillary protractile, no frenum present; scales in 55 to 65 oblique rows on side of body; mouth terminal, not inferior in position.

20a. Anal rays 13 to 18; no barbel present; mouth terminal, oblique; body compressed; lateral band of blackish color between two silvery streaks; lower sides of adults red; dorsal rays 10 or 11; greatest depth 3-1/4 to 4-1/4 times in standard length; diameter of eye 3 or 4 times in the head; length of head 4 to 4-1/2 times in the standard length.

Red sided minnow or bream. (fig. 19) Richardsonius balteatus balteatus (Richardson), p. 32, No. 16.

20b. Anal rays 7 to 105; scales in 64 to 83 oblique rows on side of body; pharyngeal teeth usually 2: 5—4: 2 or 2:4—4:212; 5 to 8 short blunt gill rakers on first gill arch.7

5Throughout this report the number of soft rays in the dorsal and anal fins are counted as follows: The first one or two rudimentary rays, closely joined to the first complete ray, are omitted. The last two rays, sometimes branching from a common base, are counted as one ray.

7All rudiments are counted.

12In Cyprinidae, the main row of teeth on each pharyngeal bone contains 4 or 5 teeth (seldom more or less); inside of this main row is a so-called "lesser row," which may contain 1 or 2 teeth or none, in the latter case being designated 0 in the formula, as, for example, "teeth 2: 4—4: 0," which means 4 teeth in each main (outer) row, and 2 teeth in one lesser row of one side and 0 teeth in the other lesser (inner) row of other side.

21a. Mouth terminal, horizontal, deeply cleft, the maxillary reaching to under the eye; 46 to 56 scale rows before the dorsal fin on the back; barbel always present on posterior edge of maxillary except on the young less than 2 inches in length; peritoneum silvery; anal of about 8 rays; dorsal of 9 or 10 rays; 16 to 20 scales above and 7 to 9 scales below the lateral line; diameter of eye 4.1 (in young) to 7.5 times in the head length; greatest depth 4.4 to 5.2 times in standard length.

Squawfish. (fig. 18) Ptychocheilus oregonensis (Richardson), p. 31, No. 15.

21b. Mouth terminal, slightly oblique, not deeply cleft, the maxillary seldom extending to the anterior margin of the eye; scale rows in front of the dorsal 32 to 44 on the back; barbel present or absent; peritoneum silvery to dusky (usually somewhat pigmented); anal rays 8 or 9 (usually 9); dorsal rays 8 to 10 (usually 9); 12 to 14 scales above and 8 to 11 scales below the lateral line.

22a. Barbel present, seldom absent on one side, located just anterior to posterior tip of the maxillary; no black caudal fin spot (near base of caudal fin rays) present in specimens over 1-1/2 inches long; interorbital space flattish; upper jaw nearly straight, the premaxillary and maxillary in a straight line and nearly reaching to under the orbit; no light streak above the wide blackish color band on sides; origin of dorsal fin just behind insertion of pelvic fin (nearer base than middle of fin).

Lake chub. (fig. 21) Couesius dissimilis. (Girard), p. 33, No. 18.

22b. Barbel absent (rarely present on one side); a black caudal fin spot near base of middle caudal rays, always present; interorbital space evenly arched; upper jaws curved, the maxillary more inclined from the horizontal axis than the premaxillary and not nearly reaching the orbit; a light streak above the wide dark color band on sides; origin of dorsal fin nearer a vertical line passing through middle of pelvic fin than one passing through its insertion.

Pearl minnow. (fig. 22) Margariscus margarieta nachtriebi (Cox), p. 34, No. 19.


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Last Updated: 22-Feb-2008