29. — Orbit diameter. — Measured as a horizontal distance from the most 

 anterior point on the fleshy margin of the orbit. 



30. — Iris diameter. — Measured as a horizontal distance from the most 

 anterior point on the margin of the (ossified) sclera. 



31. — Interorbital width. — Measured as the shortest distance between the 

 uppermost point on the fleshy margin of the orbits. 



32.— Tip of mandible to tip of bill— This character is self-explanatory. 

 Care must be taken that the jaws are well closed. 



33.— Depth of bill— Measured on the vertical passing through the tip of 

 the mandible. 



34.— Width of bill— Measured on the vertical passing through the tip of 

 the mandible. 



35. — Origin of first dorsal to edge of fin. —Measured from the origin of the 

 first dorsal fin (See first predorsal length) to the nearest tip (on dorsal edge) 

 of a dorsal spine. This measurement is connection with the anterior height of 

 the fin (see below) gives a good quantitative interpretation of the magnitude 

 of the anterior dorsal lobe. 



36. — Length of second dorsal base. — Measured from the origin of the sec- 

 ond dorsal fin (See second predorsal length) to the end of the fin base. The 

 latter point is the intersection of the posterior basal margin of the last ray 

 with the back. 



37. — Length of first anal base. — Measured from the origin of the first ana! 

 fin (See first preanal length) to the end of the anal groove. To the last (very 

 short) discernible spine in the swordfish. 



38. — Length of second anal base. — Measured according to the same 

 procedure described above for the length of the second dorsal base. 



39. — Anterior height of first dorsal. — Measured from the origin of the first 

 dorsal fin (See first predorsal length) to the tip of the lobe. 



40.— Length of middle dorsal spine— The 25th dorsal spine measured 

 (erect) from its intersection with the dorsal groove to its tip. This character is 

 a good quantitative indicator of the ontogenetic changes in height undergone 

 by the first dorsal fin. 



41. — Anterior height of second dorsal— Measured from the origin ol the sec- 

 ond dorsal fin (See second predorsal length) to the tip of its anterior lobe. 



42. — Height of first anal. — Measured according to the same procedure 

 described above for the anterior height of first dorsal. 



43. — Anterior height of second anal. — Measured according to the same 

 procedure described above for the anterior height of second dorsal. 



44. — Length of pectoral. — Measured from the origin of the pectoral fin (See 

 prepectoral length) to its tip, with the anterior basal margin of the fin perpen- 

 dicular to the body. 



45. — Length of pelvic. — Measured according to the same procedure 

 described above for the length of the pectoral. The fin should be held straight 

 and stretched to its full length. 



46. — Length of second dorsal. — Measured from the origin of the second 

 dorsal fin (See second predorsal length) to the tip of the last (suctorial) ray 

 held straight and against the middorsal line of the back. 



47. — Length of second anal. — Measured according to the same procedure 

 described above for the length of second dorsal. 



48. — Length of upper caudal lobe. — Measured from the posterior end of the 

 upper caudal keel to the tip of the upper caudal fin lobe. 



49. — Length of lower caudal lobe. — Measured according to the same 

 procedure described above for the length of upper caudal lobe, but using the 

 end of the lower keel as point of reference. 



50. — Caudal spread. — Measured between the tips of the caudal fin lobes. 



51. — Caudal angle. — Measured by joining three points of reference 

 represented by the tips of the caudal fin lobes and the middle point on the 

 posterior margin of the middle caudal ray. This character is a good quan- 

 titative indicator of the change of angulation and concavity of the caudal fin 

 among species and ontogenetically within a species. 



Counts 



1. — Dorsal spines. — The number of dorsal spines has not been widely used 

 as a taxonomic character in billfishes and there is reason to believe that most 

 of the few counts reported in the literature are not accurate. 



Careful inspection of the anterior part of the dorsal fin will show that the 

 first two or three spines are very close together, and therefore difficult or im- 

 possible to count without dissection. Very often the first and even the second 



spine is extremely short. They are easily missed if the skin covering is not 

 peeled off to the base of the fin and the spines separated with the point of the 

 knife. Posteriorly, and especially in adult marlins, the dorsal spines gradually 

 decrease in length and become very short or obsolete as the second dorsal fin 

 is approached. This condition appears to be correlated with growth, since in 

 the post-larval and juvenile stages of billfishes (Beebe, 1941; Arata, 1954) the 

 first dorsal fin is continuous with the second, but in the young adult stages a 

 gap appears externally between these two fins. This gap becomes progressive- 

 ly longer as the fish becomes older and is quite extensive in very large 

 specimens. 



Dorsal spine counts in billfishes without consideration of the above facts, 

 would be inaccurate and lead to false taxonomic interpretations, when 

 samples of widely differing age groups are compared. Dissection of the 

 anterior part of the fin obviously should always be made, and posteriorly, 

 attention should be paid to the magnitude of the gap and the resulting degree 

 of external discontinuity between the first and second dorsal fins. If the dis- 

 tance between the last dorsal spine and the origin of the second dorsal fin is 

 about equal to or somewhat greater than the distance between the last dorsal 

 spine and the preceding one. no obsolete spines are then present. It is 

 recommended that if the gap is of a magnitude indicating the existence of one 

 or more obsolete spines the dorsal spine count be followed by the sign plus 

 l + ). 



2. — Dorsal rays. — All rays are counted. In this fin the rays are easily made 

 out without dissection. 



3. — Anal spines. — Counted according to the same procedure described 

 above for the dorsal spines. The discussion given above in connection with 

 the dorsal spines also applies to the anal spines. 



4. — Anal rays. — Same procedure as described above for the dorsal rays. 



5. — Pectoral rays. — All rays are counted. Although all rays are made out in 

 this fin without dissection, care must be taken that the posterior part of the 

 fin is well spread out so that the very small posterior rays are not missed. 



References 



Arata. G. F„ JR 



1954. A contribution to the life history of the swordfish, Xiphias glad- 

 ius Linnaeus, from the south Atlantic coast of the United States and 

 the Gulf of Mexico. Bull. Mar. Sci. Gulf and Caribbean. 4 (3): 183-243, 

 figs. 1-19. 



Beebe. W. 



1941. A study of young sailfish (lstiophorus) . Zoologica, N.Y.. 26(20): 

 209-227. figs. 1-9. pis. 1-5. 

 Bl'EN. F. DE 



1950. Contribuciones a la Ictiologia, HI. La familia Istiophoridae y de- 

 scripcion de una especie uruguava (Makaira perezi de Buen). Publ. 

 Cient. S.O.Y.P. Montevideo, (5)':163-178, figs. 1-4. 



Conrad. G. M. andF. LaMonte 



1937. Observations on the body form of the blue marlin [Makaira nigri- 

 cans ampla, Poey). Bull. Amer. Mus. nat. Hist., 74 (4):207-220. 

 GODSIL. H. C. andR. D. BYERS 



1944. A systematic studv of the Pacific tunas. California Div. Fish and 

 Game. Fish Bull. (60):'l-131, figs. 1-76. 



Gregory. W. K. andG. M. Conrad 



1939. Body-forms of the Black marlin (Makaira nigricans marlina) and 

 Striped marlin (Makaira mitsukurii) of New Zealand and Australia. 

 Bull. Amer. Mus. nat. Hist., 76 (8):443-456, figs. 1-2, pis. 3-6. 

 MARR, J. C andM. B. SCHAEFER 



1949. Definitions of bodv dimensions used in describing tunas. Fish. 

 Bull. U.S., 51 (47):241-244, fig. 1. 



Morrow, J. E., JR. 



1952. Allometric growth in the striped marlin, Makaira mitsukurii, 

 from New Zealand, Pacif. Sci., 6 (11:53-58. 

 RICKER. W. E. andD. MERRIMAN 



1945. On the methods of measuring fish. Copeia, (41:184-191. 

 Rivas. L. R. 



1955. A comparison between giant bluefin tuna (Thunnus thynnus) 

 from the Straits of Florida and the Gulf of Maine, with reference to mi- 

 gration and population identity. Proc. Gulf & Carib. Fish. Inst., 1954 

 (1955):133-149, fig. 1. 



33 



ft U. S. GOVERNMENT PRINTING OFFICE: 1975-698- 164/23 REGION 10 



