Reproductive biology of tlie swordfisii 

 Xiphias gladius in tlie Straits of 

 Florida and adjacent waters 



Ronald G. Taylor 

 Michael D. Murphy 



Florida Marine Research Institute, Department of Natural Resources 

 100 Eighth Avenue SE, St. Petersburg. Florida 33701-5095 



The swordfish Xiphias gladius Lin- 

 naeus inhabits all tropical, subtrop- 

 ical, and temperate oceans of the 

 world, including the Mediterranean 

 Sea and the Gulf of Mexico. In the 

 western Atlantic, it is found from 

 Newfoundland to Argentina (Palko 

 et al. 1981, Nakamura 1985). Sword- 

 fish occur in the Florida Straits at 

 all times of the year. Prior to 1970, 

 swordfish were pursued primarily 

 by recreational fishermen. During 

 the 1970s, the fishery in Florida at- 

 tracted displaced Cuban-Americans 

 and New England longline fisher- 

 men, and by 1980 commercial land- 

 ings from the east coast of Florida 

 had reached nearly ISOOmt (Berke- 

 ley and Irby 1982). 



Little is known about the repro- 

 ductive biology of swordfish in the 

 western Adantic. Ovchinnikov (1970) 

 and Berkeley and Houde (1980) 

 reported contradictory findings on 

 male and female sizes-at-maturity. 

 Wilson (1984) reported that males 

 mature at younger ages than do 

 females in the U.S. south Atlantic. 

 Descriptions of swordfish spawning 

 season and spawning grounds have 

 been based on the temporal and 

 areal distribution of infrequently- 

 collected larvae and juveniles (Ara- 

 ta 1954, Tibbo and Lauzier 1969, 

 Markle 1974, Grail et al. 1983). Our 

 research objectives were to deter- 

 mine the size- and age-at-maturity, 

 spawning season, and approximate 

 spawning grounds of swordfish in 

 the Straits of Florida and adjacent 

 waters. Data were collected as part 



of a joint Florida Marine Research 

 Institute and University of Miami 

 investigation of the fishery and biol- 

 ogy of the swordfish. Samples gath- 

 ered during this research have been 

 used to develop a method to deter- 

 mine the ages of swordfish and to 

 describe their growth (Berkeley and 

 Houde 1984). 



Methods and materials 



Swordfish were sampled from rec- 

 reational and commercial catches 

 made off southeast Florida (Fig. 1) 

 from June 1977 through November 

 1980. Each year most of the collec- 

 tions were made April through Sep- 

 tember. Samples were taken at 

 least once each month over the 2.5 

 yr sampling period, except in De- 

 cember when no samples were 

 taken either year. Because of the 

 varied conditions of landed sword- 

 fish, a variety of length measure- 

 ments (to the nearest cm) were 

 taken: total length (TL), distance 

 from the tip of the bill to the mid- 

 point of the line connecting the 

 distal edges of the caudal-fin lobes; 

 fork length (FL), from the tip of the 

 bill to the distal end of the central 

 ray of the caudal fin; lower jaw to 

 fork length (LJFL), from the tip of 

 the lower jaw to the distal end of the 

 central ray of the caudal fin; eye to 

 fork length (EFL), from the poste- 

 rior margin of the eye's bony orbit 

 to the distal end of the central ray 

 of the caudal fin; and trunk length 

 (TRNKL), from the posterior mar- 



gin of the gill cavity to the point of 

 least circumference of the caudal 

 peduncle. Lower jaw to fork length 

 is used throughout this paper unless 

 otherwise noted. For fish measured 

 only for TL, FL, EFL, or TRNKL, 

 LJFL was estimated using the 

 appropriate regression equation 

 (Table 1). Whole weight (W) was 

 determined to the nearest pound 

 and converted to kilograms for our 

 analyses. Portions of ovaries and 

 testes were collected and preserved 

 in Davidson's fixative (Humason 

 1972). Whole gonads, macroscop- 

 ically judged ripe or mature based 

 on the presence of transparent 

 eggs, were preserved and then 

 weighed to the nearest gram. 



Swordfish maturity was described 

 using histological features to define 

 gonadal development. Subsamples 

 of preserved gonads were embedded 

 in paraffin, sectioned at Gj^m, stained 

 with Mayer's haematoxylin and 

 eosin, and mounted for microscopic 

 examination. Swordfish were as- 

 signed to one of eight developmen- 

 tal classes following Murphy and 

 Taylor (1990) and based on the ap- 

 pearance of histological features 

 described by Grier (1981) for males 

 and Wallace and Selman (1981) 

 for females. These developmental 

 classes and the mean observed 

 oocyte diameters are (1) Immature, 

 <20^im- (2) Developing, llt^m; (3) 

 Maturing, IGO^m; (4) Mature, 434 

 Mm; (5) Gravid, 723 ^m; (6) Spawn- 

 ing/Partially Spent, 823 Mm; and (7) 

 Spent, 181 Mm. The relationship 

 between swordfish maturity and 

 length was described for each sex 

 using maturity data for fish grouped 

 into 10 cm size-classes. A logistic 

 distribution function was fit to the 

 percentages of mature fish ( > Glass 

 4) and the midpoints of their size- 

 classes (Saila et al. 1988) in order 

 to predict a maturity schedule. A 

 similar distribution function was 

 generated for maturity against age. 



Manuscript accepted 2 July 1992. 

 Fishery Bulletin, U.S. 90:809-816 (1992). 



809 



