Field Key to Sharks Encountered in the U.S. Atlantic Bottom Longline Shark Fishery and by Recreational Anglers

© George Burgess, Florida Program for Shark Research

How to Use this Key:

  1. Start with the first question. Decide whether the statment in the first box (1a) or the the second box (1b) best describes the characteristics of the shark you are trying to identify. (See this page on shark anatomy if you need help.)
  2. Click on the link in the row that best matches your shark. Your choice will lead you to a link to the species profile page for that shark or the next appropriate pair of questions.
  3. Work through the questions, each time choosing the characteristic that best matches your shark from the two choices. This will lead you to the final choice which identifies the shark.
1a) Body flattened dorso-ventrally, skate-like in appearance Squatina dumeril - Atlantic angel shark
1b) Body round in cross section Go to question 2

2a) Seven gill slits, single dorsal fin Heptranchias perlo - sharpnose sevengill shark
2b) Six gill openings, single dorsal fin Go to question 3
2c) Five gill openings, two dorsal fins Go to question 4

3a) Snout short, blunt and broad; eye small; distance between rear base of dorsal fin and origin of caudal fun about 1.5 to 2.0 times length of dorsal fin base; lower jaw with six rows of teeth Hexanchus griseus - bluntnose sixgill shark
3b) Snout more pointed and narrow; eye large; distance between rear base of dorsal fin and origin of caudal fin about 2.5 to 3 times length of dorsal fin base; lower jaw with five rows of teeth Hexanchus nakamurai - bigeye sixgill shark

4a) Anal fin absent Go to question 5
4b) Anal fin present Go to question 9

5a) No spines on dorsal fins Echinorhinus brucus - bramble shark
5b) Both dorsal fins with spines Go to question 6

6a) First dorsal spine over or posterior to inner corner of pectoral fin; midpoint of base of pelvic fin much nearer to origin of second dorsal fin than to rear base of first dorsal fin Go to question 7
6b) First dorsal spine almost over midpoint of inner margin of pectoral fin; midpoint of base of pelvic fin about midway between rear base of first dorsal fin and origin of second dorsal fin Go to question 8

7a) First dorsal fin noticeably larger than second dorsal fin; anterior nasal flap with small and narrow secondary lobe; usually conspicuous white spots present on sides of body Squalus acanthias - spiny dogfish
7b) Second dorsal fin nearly as large as first dorsal fin; anterior nasal flap with large and broad secondary lobe, almost barbel-like; color dark without conspicuous white spots on sides of body Cirrhigaleus asper - roughskin dogfish

8a) Inner margins of pectoral fins deeply concave, inner corners acutely pointed. Squalus cubensis - Cuban dogfish
8b) Inner margins of pectoral fins weakly concave, inner corners at approximately right angles Squalus blainville - longnose spurdog

9a) Caudal peduncle with one or more keels or ridges Go to question 10
9b) Caudal peduncle without keels or ridges Go to question 17

10a) Two keels present, a strong keel on caudal peduncle and a short secondary keel on caudal base Lamna nasus - porbeagle
10b) One keel or ridge on caudal peduncle, no secondary keel on caudal base. Go to question 11

11a) Mouth located on tip of snout; coloration a series of round spots and narrow transverse stripes; three to four large ridges along back and sides Rhincodon typus - whale shark
11b) Mouth inferior; color not as above; no such ridges along back and sides Go to question 12

12a) Keel on caudal peduncle a weakly developed ridge Go to question 13
12b) Keel on caudal peduncle well developed Go to question 14

13a) Spiracle present; first dorsal fin originates even with rear bases of pectoral fins; pectoral fins moderately long; coloration irregular bands or elongated spots Galeocerdo cuvier - tiger shark
13b) Spiracle absent; first dorsal fin originates well past rear bases of pectoral fins; pectoral fins very long; coloration uniformly cobalt blue Prionace glauca - blue shark

14a) Gill slits long, extending almost full height of head; teeth minute and hooked Cetorhinus maximus - basking shark
14b) Gill slits shorter, not extending full height of head; teeth large, prominent and erect Go to question 15

15a) Origin of anal fin placed well behind rear base of second dorsal fin; all teeth strongly serrated, the uppers flat and broadly triangular; black spot usually present in axils of pectoral fins; coloration dark grey above and laterally with a white belly and underside of snout Carcharodon carcharias - white shark
15b) Origin of anal fin placed at mid or rear base of the second dorsal fin; teeth smooth-edged, not greatly flattened, narrowly triangular and blade-like; black axil spot always lacking; coloration cobalt blue above and laterally with belly and underside of snout white Go to question 16

16a) Snout greatly pointed; pectoral fins much shorter than head; anal fin origin under mid base of second dorsal fin; symphysial teeth of both jaws recurved; eyes small Isurus oxyrinchus - shortfin mako
16b) Snout bluntly pointed; pectoral fins as long as head; anal fin origin under rear base of second dorsal fin; symphysial teeth straight or only slightly recurved; eye large Isurus paucus - longfin mako

17a) Head flattened dorso-ventrally and expanded laterally, hammer- or spade-shaped Go to question 18
17b) Head not dorso-ventrally flattened and expanded laterally Go to question 21

18a) Head margin rounded, spade-shaped Sphyrna tiburo - bonnethead
18b) Head hammer-shaped Go to question 19

19a) Head margin broadly convex without a noticeable indentation at tip of snout Sphyrna zygaena - smooth hammerhead
19b) Head margin broadly convex to straight with noticeable indentation at tip of snout Go to question 20

20a) Second dorsal fin small, free rear tip about twice the vertical height of fin; first dorsal fin tall, narrowly pointed, posterior margin strongly falcate; pelvic fin margin straight to weakly falcate Sphyrna lewini - scalloped hammerhead
20b) Second dorsal fin large, free rear tip,shorter or equal to vertical height of fin; first dorsal broadly triangular, posterior margin nearly straight to slightly falcate; pelvic fin margin strongly falcate Sphyrna mokarran - great hammerhead

21a) Dorsal lobe of caudal fin greatly elongated, being nearly as long as the distance from tip of snout to precaudal pit Go to question 22
21b) Dorsal lobe of caudal fin not elongated, being much shorter than the distance from tip of snout to precaudal pit. Go to question 23

22a) Head flattened between eyes with a pronounced, deep groove on nape above gill slits; eyes very large, horizontal diameter is less than vertical diameter, with orbits extending onto top of head; rear tip first dorsal fin origin lies midway between rear pectoral fin base and terminates anterior to origin of pelvic fins Alopias superciliosus - bigeye thresher
22b) Head arched between eyes, no grooves present on nape above gill slits; eEye smaller, horizontal diameter is approximately equal to vertical diameter, not extending onto top of head; rear tip first dorsal fin origin lies much closer to rear pectoral fin base than toterminates over or beyond origin of pelvic fins Alopias vulpinus - thresher

23a) First and second dorsal fins of about equal in size Go to question 24
23b) The two dorsal fins unequal in size, the first noticeably larger than the second Go to question 28

24a) A low dermal ridge present on midline of dorsal surface between first and second dorsal fins Go to question 25
24b) No low dorsal dermal ridge present on midline of dorsal surface between first and second dorsal fins Go to question 26

25a) Upper labial furrows shorter than lower labial furrows; corner of lower lobe of caudal fin pointed and directed rearward; distal margin of pectoral fin deeply concave Mustelus norrisi - narrowfin smoothhound
25b) Upper labial furrows slightly longer than lower labial furrows; corner of lower lobe of caudal fin broadly rounded; distal margin of pectoral fin nearly straight Mustelus canis - smooth dogfish

26a) Head pointed; large pointed and recurved teeth protrude from mouth Carcharias taurus - sand tiger shark
26b) Head blunt; teeth pointed but not recurved or protruding from mouth Go to question 27

27a) Large and obvious barbel present on margin of each nostril; no precaudal pit; teeth pavement-like with central ridge Ginglymostoma cirratum - nurse shark
27b) No barbel on margin of each nostril; precaudal pit present; teeth erect with serrations on larger individuals, smooth on young Negaprion brevirostris - lemon shark

28a) Dorsal, pectoral, and caudal fins tipped with white (black tipped in juveniles); first dorsal fin broadly rounded; pectoral fins large, paddle-shaped with rounded tips Carcharhinus longimanus - oceanic whitetip shark
28b) Fins not white tipped, first dorsal and pectoral fins not broadly rounded Go to question 29

29a) Anal fin origin anterior to second dorsal fin origin; larger individuals with white lateral spotting; pectoral fins with white margins Rhizoprionodon terraenovae - Atlantic sharpnose shark
29b) Anal fin origin posterior to or even with second dorsal fin origin; lateral white spotting lacking at all sizes Go to question 30

30a) Low ridge present between first and second dorsal fins Go to question 31
30b) Low ridge absent between first and second dorsal fins Go to question 37

31a) Length of fin near tip of second dorsal fin more than two times the vertical height of the fin; first dorsal fin short with rounded tip Carcharhinus falciformis - silky shark
31b) Length of free tip of second dorsal fin in two times or less vertical height of the fin; first dorsal fin taller and not notably rounded Go to question 37

32a) Snout long and pointed, distance between nostrils on underside of snout is 0.5-0.6 the length of the snout; eyes large and green in life Carcharhinus signatus - night shark
32b) Snout shorter and broader, distance between nostrils on underside of snout is greater than 0.6 the length of the snout (tip of snout to mouth); eyes smaller and never green in life Go to question 33

33a) First dorsal fin located forward on body, its origin over or anterior to pectoral fin axil (or at least closer to the axil than to its free rear tip) Go to question 34
33b) First dorsal fin located farther back on body, its origin over or posterior to the free rear tip of the pectoral fin (or at least closer to free rear tip than to axil) Go to question 35

34a) First dorsal fin large, vertical height greater than 10% of total length; snout moderately long and rounded, its length about half the height of the first dorsal fin Carcharhinus plumbeus - sandbar shark
34b) First dorsal fin smaller, vertical height less than 10% of total length; snout longer and rounded or bluntly pointed, its length almost the same as the height of the first dorsal fin Carcharhinus altimus - bignose shark

35a) Free rear tip of second dorsal fin short, its length about equal to the height of the fin; color grayish brown to olive gray in life with pronounced dark edging on margins of caudal fin, especially the lower lobe, and on tips of anal and second; snout short and broadly rounded; upper teeth with narrow cusps, 13 upper teeth and 12 lower teeth on each side of the jaw Carcharhinus perezi - Caribbean reef shark
35b) Free rear tip of second dorsal fin longer, its length nearly 1.5 the height of the fin; color grayish brown to gray in life without pronounced dark edging on margins of caudal fin, especially the lower lobe, and on tips of anal and second dorsal fin;dorsal fin; snout moderately long; upper teeth with narrow cusps, 13 upper teeth and 12 lower teeth on each side of the jaw Go to question 36

36a) First dorsal fin high with nearly straight anterior margin and pointed tip, snout length about 3/4 or less of the fin height in all sizes; second dorsal fin somewhat larger, length of its free rear tip 1.3-1.7 times its height Carcharhinus galapagensis - Galapagos shark
36b) First dorsal fin lower with a rounded anterior margin and slightly rounded tip, snout length about equal to or greater than the fin height in all but large adults; size of second dorsal fin somewhat smaller, length of its free rear tip 1.6-2.1 times its height Carcharhinus obscurus - dusky shark

37a) Snout short and broadly rounded,length of snout much shorter than width of mouth; upper teeth broadly triangular and serrated, without notches on outer margins Carcharhinus leucas - bull shark
37b) Snout longer, length of snout equal to or longer than width of mouth; upper teeth erect and smooth or with fine serrations, or with narrow, oblique cusps and serrated edges Go to question 38

38a) Black or dusky spot on tip of snout, more prominent in young and more diffuse in larger individuals; coloration yellowish green to brownish in life, fading to grey after death; teeth with narrow, oblique cusps and serrated edges Carcharhinus acronotus - blacknose shark
38b) No black or dusky spot on tip of snout; teeth erect and smooth or with fine serrations Go to question 39

39a) No black or dusky tips on fins; teeth erect, narrow, and smooth Carcharhinus isodon - finetooth shark
39b) Black or dusky tips on fins; teeth with broader base and fine serrations Go to question 40

40a) Anal fin with black tip except in young (less than 70 cm total length); first dorsal fin origin lies at level of or behind free tip of pectoral fin; snout long; height of first dorsal fin less than length of snout except in large adults, when it become about the same or slightly larger; eye small, horizontal diameter is one-fourth or less than the length of first gill opening Carcharhinus brevipinna - spinner shark
40b) Snout shorter; height of first dorsal fin always greater than length of snout, snout about 2/3 of first dorsal fin height in large adults; eye larger, horizontal diameter one third greater than length of first gill opening Carcharhinus limbatus - blacktip shark