FIRST RECORD OF 



THE LONGFIN MAKO, ISURUS PAUCUS, 



IN THE GULF OF MEXICO 



The longfin mako, Isurus paucus, (Guitart-Manday 

 1966) is a large, pelagic shark that has been reported 

 from the western Indian, central Pacific, eastern 

 North Atlantic, and the western North Atlantic 

 Oceans (Compagno 1984). Guitart-Manday (1975, 

 cited by Dodrill and Gilmore 1979) described the 

 longfin mako as a relatively common catch of pelagic 

 longliners off northwest Cuba. They are usually cap- 

 tured off the continental shelf at depths of 60-120 

 fathoms and infrequently at 10-50 fathoms. Dodrill 

 and Gilmore (1979) reported the first North Ameri- 

 can continental longfin mako, found beached in the 

 surf at Melbourne Beach, FL. This paper reports 

 the first recorded occurrence of the longfin mako 

 in the Gulf of Mexico. 



A large female /. paucus was collected 1 April 

 1985 by longline fisherman, 80 mi south of Panama 

 City, FL Gat. 28°55'N, long. 85°35'W) near the sur- 

 face, over 300 fathoms of water. Standard length 

 (precaudal length) measured 313.0 cm and fork 

 length measured 342.0 cm. Total length could not 

 be measured directly because of the sharks position 

 on the boat deck and was estimated using a ratio 

 of total length to fork length (TL/FL = 1.152) cal- 

 culated from 7 large /. paucus (Harold Pratt 1 ). Using 

 this ratio, total length was estimated to be ca. 390 

 cm. Although no embryos were present in the ovi- 

 duct, this fish appeared reproductively mature. The 

 oviducts were 3-4 cm in diameter and ovarian eggs 

 measured 2-3 mm in diameter. Gilmore (1983) pro- 

 posed the reproductive strategy of /. paucus to be 

 oviphagous, as remnants of yolk were found in the 

 digestive tract and mouth of an examined embryo. 



The ventral surface of the snout and gill areas of 

 our shark exhibited a dark grey coloration. Garrick 

 (1967) reported this coloration as an important 

 distinguishing characteristic between /. paucus and 

 the shortfin mako, /. oxyrinchus, which exhibits a 

 creamy white coloration in that area. Gilmore (1983) 

 reported the dusky coloration to be more extensive 

 in larger /. paucus. 



Pectoral fin length of our shark measured 80.6 cm. 

 Gilmore (1983) compared an adult and embryo /. 

 paucus and found that the pectoral fin length 

 represented a greater percentage of SL in the em- 

 bryo (31% of SL) than in the adult (28% of SL). Our 



Gulf of Mexico specimen was slightly larger than the 

 specimen reported by Gilmore (1983) (313.0 cm vs 

 303.5 cm SL), and the pectoral fin represented 26% 

 of SL. Guitart-Manday (1966) examined smaller /. 

 paucus— 195, 203, and 226 cm TL— and found pec- 

 toral fin length as percent total length to be 30.4%, 

 30.0%, and 29.2%, respectively. For this specimen, 

 pectoral fin length as percent TL was about 21%. 

 It appears that as /. paucus increase in length, the 

 pectoral fins do not increase proportionately, result- 

 ing in reduced pectoral length to total length ratios 

 in larger sharks. 



This record suggests that the longfin mako at least 

 occurs infrequently in the northern Gulf of Mexico. 

 Three male /. paucus (191, 193, and 220 cm SL) cap- 

 tured 16 April 1985 off the Mississippi River (lat. 

 27°35'N, long. 89°55'W) further supports this sug- 

 gestion (Stephen Branstetter 2 ). These captures ex- 

 tend the known range of this species well into the 

 northern Gulf of Mexico. 



Acknowledgments 



We would like to extend a most sincere thanks to 

 Lew Bullock of the Florida Department of Natural 

 Resources for his help in examining this shark. We 

 are grateful to Stephen Branstetter and Wes Pratt 

 for reviewing the manuscript and providing unpub- 

 lished data. 



Literature Cited 



Compagno, L. J. V. 



1984. FAO species catalogue. Vol. 4. Sharks of the world. An 

 annotated and illustrated catalogue of sharks species known 

 to date. Part 1. Hexanchiformes to Lamniformes. 

 FAO Fish. Synop. 125, Vol. 4(Pt. 1), 249 p. 

 Dodrill, J. W., and R. G. Gilmore. 



1979. First North American continental record of the longfin 

 mako (Isurus paucus Guitart-Manday). Fla. Sci. 42:52-58. 

 Garrick, J. A. F. 



1967. Revision of sharks of genus Isurus with description of 

 a new species (Galeoidea, Lamnidae). Proc. U.S. Natl. Mus. 

 118:663-690. 

 Gilmore, R. G. 



1983. Observations on the embryos of the longfin mako, 

 Isurus paucus and the bigeye thresher, Alopias super cili- 

 osus. Copeia 1983:375-382. 

 Guitart-Manday, D. 



1966. Nuevo nombre para una especie de tibur6n del genero 

 Isurus (Elasmobranchii:Isuridae) de aguas Cubanas. Poe- 

 yana Ser. A, No. 15, 9 p. 

 1975. Las pesquerias pelagico-oceanicas de corto radio de ac- 

 tion en la region noroccidental de Cuba. Oceanogr. Inst., 



'Harold Pratt, Northeast Fishery Center Narragansett Labora- 

 tory, National Marine Fisheries Service, NOAA, South Ferry 

 Road, Narragansett, RI 02882-1199, pers. commun. June 1985. 



2 Stephen Branstetter, Department of Wildlife and Fisheries 

 Science, Texas A&M University, College Station, TX 77843-2258, 

 pers. commun. August 1985. 



748 



FISHERY BULLETIN: VOL. 84, NO. 3, 1986. 



