Temperate and tropical tunas

1. 1. Ventral finlets silver or dark in color

      Go to 2
   2. Ventral finlets Yellow color

      Go to 3
2. 1. Pectoral fin reached second dorsal fin/No horizontal stripes in lower side of the body

      Albacore
   2. Pectoral fin does not reach the second dorsal fin/4-6 horizontal stripes on lower side of the body (In both sides)

      Skipjack tuna
3. 1. Pectoral fin extends beyond origin of 2nd dorsal fin/Pattern of alternating light lines and dots on belly region

      Yellowfin tuna
   2. Pectoral fin does not extend beyond origin of 2nd dorsal fin/No dot and line patterns in the belly region

      Bigeye tuna

BillFish

1. 1. Upper bill flat/Single caudal keel

      Sword fish
   2. Upper bill round/Double caudal keel

      Go to 2
2. 1. 1 ^st Dorsal fin height at midbody more than body depth

      Sail fish
   2. 1 ^st Dorsal fin height at midbody less than or equal to body depth

      Go to 3
3. 1. 1 ^st Dorsal fin height at midbody equal to body depth

      Striped marlin
   2. 1st Dorsal fin height at midbody half to body depth

      Go to 4
4. 1. Rigid sickle shaped pectoral fins

      Black marlin
   2. Pectoral fin folds back

      Blue marlin

Neritic tuna and mackerels (Seer fishes)

1. 1. Lateral line abruptly downwards below the 2nd dorsal fin

      Go to 2
   2. Lateral line not abruptly downwards below the 2nd dorsal fin

      Go to 3
2. 1. Sides silvery grey marked with transverse vertical bars of darker grey

      Narrow-barred Spanish mackerel
   2. Sides silvery white with several longitudinal rows of round dark brownish spots scattered in about 3 irregular rows

      Indo-Pacific king mackerel
3. 1. Tip of second dorsal and anal fins washed with yellow

      Longtail tuna
   2. Pattern of 15 or more dark bars or wavy lines, oblique to nearly horizontal, in the scale less area above lateral line

      Go to 4
4. 1. Lack of space between dorsal fins/2-5 Dark spots above the ventral fin

      Kawakawa
   2. Two dorsal fins separated by a large space/No dark spots above the ventral fin

      Go to 5
5. 1. Short pectoral fin but extending posterior to beginning scale less area above corselet

      Frigate tuna
   2. Short pectoral fin which does not reach the beginning of scale less area above corselet

      Bullet tuna

Sharks

1. 1. Lunate caudal fin

      Short fin mako shark
   2. Hetero-cercal caudal fin

      Go to 2
2. 1. Dorsal caudal lob nearly as long as rest of the body

      Go to 3
   2. Dorsal caudal not long as rest of the body

      Go to 4
3. 1. Wide dorsal tip

      Big eye thresher shark
   2. Narrow dorsal tip

      Pelagic thresher shark
4. 1. The points pectoral fins and the first dorsal fin spots white colored

      Oceanic whitetip shark
   2. The points pectoral fins and the first dorsal fin spots are dusky

      Go to 5
5. 1. Broad, narrow bladed hammerhead

      Scalloped hammerhead shark
   2. Non-hammer shape head

      Go to 6
6. 1. Second dorsal less than a third the size of the first dorsal/Blue color dominant body

      Blue shark
   2. Non-hammer shape head

      Silky shark