1. ACDU Acanthurus dussumieri Acanthurus xanthopterus 65 cm (30 cm avg) NAAN Naso annulatus Acanthurus mata 50 cm (30 cm avg) ACXA. Yellow pectoral fins. Frequently white ring at tail base. Often pale blue area around caudal spine. Largest surgeon. ACMT. Black spine. Upper lip yellowish. Small blackish spot at upper end of gill opening.

2. Naso caesius 62 cm (40 cm avg) Naso hexacanthus 75 cm (35 cm avg) NACA. Can change to pattern of indistinct round to vertically elliptical blotches on upper half of body. No dark margin on gill cover. NAHE. Black band marking and black margin on gill cover. Margin of lower lip white. Blue caudal fin.

3. Naso vlamingii 60 cm (35 cm avg) Naso unicornis 70 cm (40 cm avg) Naso brevirostris 50 cm (30 cm avg) NABR. Broad based tapering horn. NAVL. Blue lips and blue band in front of eye. NAUN. Tail spines blue. Horn short; does not project past mouth.

4. ACNI. Acanthurus nigricauda 40 cm (23 cm avg) Long black bar behind eye to above pectoral fin, thin streak on rear body to tail spine. ACLU. Acanthurus leucocheilus 45 cm (26 cm avg) Pale lips and pale band on chin. Yellow sub-border on pectoral fin, white tail spine. ACPY. Acanthurus pyroferus 25 cm (18 cm avg.) Curving black band from chin to upper edge of gill cover; orange patch above pectoral fin base.

5. ACMA Acanthurus maculiceps 20 Acanthurus maculiceps 40 cm (30 cm avg) Acanthurus nigrofuscus 23 cm (10 cm avg) Ctenochaetus marginatus 22 cm (15 cm avg) ACNF. Head, nape, chest with small orange spots. Lips blackish Black spot at rear base of last dorsal and anal fin rays. CTMA. Pale blue margin on base of anal fin. Fins finely striped, except pectorals, which have spots. Small blue spots on head and body ACMC. Black streak behind upper edge of gill cover. Black margin on tail spine. Often white ring at tail base.

6. Ctenochaetus cyanocheilus 20 cm (13 cm avg) Ctenochaetus strigosus 18 cm (13 cm avg) Ctenochaetus striatus 28 cm (11 cm avg) Nape and around eye with small, orange-yellow spots. May display small black spot at rear base of dorsal fin. CTCY. Blue lips, chest with a bluish cast. Narrow yellow ring around eye.

7. Ctenochaetus flavicauda 16 cm (9 cm avg) Ctenochaetus hawaiiensis 28 cm (25 cm avg) CTHA. Fine pale-greenish lines over the head and along the body, but appear almost black at a distance. CTFL. Conspicuous white to yellowish tale. Rim of posterior half of eye bright yellow.

8. Juveniles CTST CTFL CTSR

9. Mimics ACPY CEVR CEFL AcanthuridModel Lack of gill cover spine.