1. Swordfish/Billfish Identification
Southeast Fisheries Science Center Pelagic Observer Program - Billfish Identification

2. Billfish/swordfish Xiphiidae Istiophoridae swordfish
single caudal keel
pelvic fins absent
‘bill’ section flat (or depressed)
1st & 2nd dorsal fins separate
scales absent
billfish, marlins, spearfish, sailfish
two caudal keel
pelvic fins present (rigid & tapering)
‘bill’ section round
1st & 2nd dorsal fins close
scales present

3. XIPHIIDAE – SWORDFISH Xiphias gladius SWO Common size:1.2-1.6 m
Surface smooth
Bill depressed in cross section
Dorsal fins well separated
No teeth
Pelvic fins absent
Single strong
caudal keel
No scales on body 3

4. XIPHIIDAE – SWORDFISH Xiphias gladius SWO

5. XIPHIIDAE – SWORDFISH Xiphias gladius SWO
Hawaii Longline Observer Program -

6. ISTIOPHORIDAE – SAILFISH Istiophorus albicans SAI Common size:1.0-1.5m
Blue-black, high, sail-like 1st dorsal fin with dark spots, may be folded back
From Nakumura 1985: Pectoral fins and caudal fin long in immature specimens to about 90 cm body length (Fig. 26); attains smaller size (about 60 kg maximum body weight).
Field Marks: First dorsal fin sail-like and remarkably higher than greatest body depth; pelvic fins very
long, nearly reaching to anus, with a well developed membrane; pectoral and caudal fins long compared with those
of Istiophorus platypterus in young fish up to about 90 cm body length
Pelvic fins long & narrow, much longer than pectoral fins, extending at least 2/3 to ¾ of body length
Body slender; usually with vertical bars on sides 4

7. ISTIOPHORIDAE – SAILFISH Istiophorus albicans SAI
Southeast Fisheries Science Center Pelagic Observer Program - Billfish Identification 1

8. ISTIOPHORIDAE – SAILFISH Istiophorus albicans SAI

9. ISTIOPHORIDAE – SAILFISH Istiophorus albicans SAI

10. ISTIOPHORIDAE – BLUE MARLIN Makaira nigricans BUM Common size:2.5m
Dorsal and pectoral fins pointed
Most of dorsal fin low; blue-black & no spots
Field Marks : Body not very compressed; nape highly
elevated; height of anterior lobe of first dorsal fin less than
greatest body depth; lateral line system chickenwire-shaped
Pelvic fins short (no longer than pectoral fins)
lateral line system chickenwire-shaped
Body robust, may grow very large 4

11. BLUE MARLIN - BUM Makaira nigricans
Photo from fishbase: ©Baumeier, Eduardo
Double
caudal keel

12. ISTIOPHORIDAE – BLUE MARLIN Makaira nigricans BUM
Photo: Simon Gulak
Photo: Simon Gulak

13. ISTIOPHORIDAE – BLUE MARLIN Makaira nigricans BUM
Photo: Simon Gulak
Photo: Clay Archambault (from WWF-South Africa Responsible
Fisheries Program training materials

14. *Occasional migrant in southeast Atlantic
ISTIOPHORIDAE –
BLACK MARLIN
Makaira indica
BLM
Common size: m
Most of dorsal fin low; blue-black & no spots
Dorsal and pectoral fins pointed
Dorsal is ½ or LESS greatest body depth
Pectoral fin rigid & sickle shaped; not foldable against body
Field Marks : Body not very compressed; nape highly elevated; height of anterior lobe of first dorsal fin
smaller than greatest body depth; second dorsal fin slightly forward of second anal fin; pectoral fins rigid, not adpressible against sides of body.
Lateral line simple
Reticulate (chain pattern) lateral line in juveniles 4
*Occasional migrant in southeast Atlantic 14

15. BLM

16. ISTIOPHORIDAE – BLACK MARLIN Makaira indica BLM
Photo: from WWF-South Africa Responsible
Fisheries Program training materials

17. ISTIOPHORIDAE – WHITE MARLIN Tetrapturus albidus WHM Common size:1.5m
Dorsal fin rounded with many dark spots. Posterior portion of dorsal fin relatively close to body.
Lateral line arched over pectoral fins
Tip of first dorsal fin, pectoral fins and first anal fin rounded
First dorsal fin spotted; scales on midbody pungent, each scale elongate with 1 or 2 spines (Fig.35) Tetrapturus albidus
Field Marks : Anterior lobe of first dorsal fin rounded and higher than
remainder of fin, the height decreasing gradually backward; anus situated near origin
of first anal fin, the distance between them smaller than half of first anal fin height.
Pelvic fins short (no longer than pectoral fins)
Pectoral, anal & 1st dorsal fins rounded
Anal opening very close to anal fin 4

18. ISTIOPHORIDAE –
WHITE MARLIN
Tetrapturus albidus
WHM

19. ISTIOPHORIDAE – WHITE MARLIN
Tetrapturus albidus WHM
©Chow, Seinen (Fishbase)

20. ISTIOPHORIDAE – WHITE MARLIN Tetrapturus albidus WHM

21. Tetrapturus pfluegeri SPF Common size:1.5m
ISTIOPHORIDAE –
LONGBILL SPEARFISH
Tetrapturus pfluegeri
SPF
Common size:1.5m
No spots on dorsal fin. Posterior portion relatively high off body.
Upper jaw shorter than other bilfish
Pelvic fins slightly longer than pectoral fins
Pectoral fins generally wide & long
Nakamura Bill long, its length (X) usually equal to, or longer than, head length (Y); pectoral fins wide and long, more than 18% body length
Field Marks : Bill long, its length usually equal to or slightly longer than head
length; pectoral fins wide, long and rounded, longer than 18% of body length; anus
situated far anterior to first anal fin origin, the distance between anus and anal fin
origin nearly equal to anal fin height.
Anal opening about the same distance as anal fin height 4

22. ISTIOPHORIDAE –
LONGBILL SPEARFISH
Tetrapturus pfluegeri
SPF
©Jueguen Santiago Barreiro (Fishbase)

23. Tetrapturus angustirostris SSP Common size:1.35m
ISTIOPHORIDAE –
SHORTBILL SPEARFISH
Tetrapturus angustirostris
SSP
Common size:1.35m
No spots on dorsal fin. Posterior portion relatively high off body.
Bill very short (<15% length)
Pectoral fins narrow & short
Pelvic fins longer than pectoral fins
Field Marks : Bill very short, usually less than 15% of body length; pectoral fins narrow and short, less than 15% of body length; distance between anus and anal fin oriyin nearly equal to anal fin height
2b) First dorsal fin (X) lower than body depth (Y) at level of midbody, not saillike; pelvicfin rays short, well separate from origin of anal fin, with moderately developed membrane (Fig.
4a. Height of anterior lobe of first dorsal fin (X) s l i g h t l y g r e a t e r than, or nearly equal to, body depth (Y); nape slightly elevated or not elevated (Fig.28); body well compressed laterally; vertebrae 12+12=24
5a. Anterior lobe of first dorsal fin slightly higher than rest of fin which remains of about equal height almost to the end (Figs 27,30,31,32); anus situated far anterior to first anal fin origin (Fig.29), the distance between them (X) greater than height of first anal fin (Y)
6a. Bill short, its length (X) usually equal to, or shorter than, head length (Y); pectoral fins narrow and short, less than 18% of body length (Figs 30, 31)
7a. Bill very short, less than 15% of body length
Anal opening about the same distance as anal fin height
*Occasional migrant in southeast Atlantic 4

24. Tetrapturus angustirostris SSP
ISTIOPHORIDAE –
SHORTBILL SPEARFISH
Tetrapturus angustirostris
SSP

25. No spots on dorsal fin. Posterior portion relatively high off body.
ISTIOPHORIDAE –
ROUNDSCALE SPEARFISH
Tetrapturus georgii
RSP
Common size:>1.0m
No spots on dorsal fin. Posterior portion relatively high off body.
Tip of first dorsal fin, pectoral fins and first anal fin rounded
Scales on midbody soft and rounded
Tip of first dorsal fin, pectoral fins and first anal fin rounded
First dorsal fin unspotted; scales on midbody s o f t and rounded (Fig.34) Tetrapturus georgei
Field Marks : First dorsal fin unspotted; tips of first dorsal and anal fins rounded; distance between anus and anal fin origin nearly equal to half of anal fin height; scales on mid-body soft and round.
Anal opening about half the distance of anal fin height 4

26. Sexing Swordfish Male Female
triangular in shape (cross section) & smooth exterior
in cross section, contains a small opening (lumen) with smooth edges
no granules visible
Color: white to pink
oval/circular shape (cigar or sausage shaped)
rough (striated) external appearance
in a cross section, the presence of a lumen (opening) near the center with somewhat rough edges
small granules (eggs) frequently present
Color: variable, ranges from gray (indicating immature egg production) to orange (indicating near spawning).
Generally, swordfish and tuna over 250 pounds are female.
Photos from : NMFS. 2007b. Northeast Fisheries Observer Program, Fisheries Observer Program Manual. NOAA Fisheries Service, Northeast Fisheries Science Center, Woods Hole, MA.

27. Sexing Swordfish
Male
Southeast Fisheries Science Center Pelagic Observer Program - Billfish Identification 1

28. Southeast Fisheries Science Center Pelagic Observer Program - Billfish Identification1

29. Southeast Fisheries Science Center Pelagic Observer Program - Billfish Identification1

30. Southeast Fisheries Science Center Pelagic Observer Program - Billfish Identification1

31. Sexing Billfish
Arrow pointing to location of gonads when fish is split open. These gonads are ovaries (female).
Hawaii Longline Observer Program Field Manual Honolulu, HI, Manual Version: LM.01.10 1

32. Sexing Billfish Mature ovaries (female)
Hawaii Longline Observer Program Field Manual Honolulu, HI, Manual Version: LM.01.10 1

33. Sexing Billfish
Cross section of an immature ovary. Notice the granulated texture of the lumen.
Hawaii Longline Observer Program Field Manual Honolulu, HI, Manual Version: LM.01.10 1

34. Sexing Billfish Arrows pointing to testes
Hawaii Longline Observer Program Field Manual Honolulu, HI, Manual Version: LM.01.10 1

35. Sexing Billfish
Cross section of a testis. Notice the smooth texture compared to the granulated texture of the ovary.
Hawaii Longline Observer Program Field Manual Honolulu, HI, Manual Version: LM.01.10 1

36. References
Southeast Fisheries Science Center Pelagic Observer Program - Atlantic Tunas and Tuna-like Species Identification.
Schneider 1990 Gulf of Guinea Field Guide
Chapman, L., P. Sharples, D. Brogan, A. Desurmont, S. Beverly, and W. Sokimi Marine species identification manual for horizontal longline fishermen. Secretariat of the Pacific Community, New Caledonia.
Nakamura, I FAO Species Catalogue. Vol. 5. Billfishes of the world. An annotated and illustrated catalogue of marlins, sailfishes, spearfishes and swordfishes known to date. FAO Fish. Synop. 125(5):65 p.