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Fishery Bulletin 90(4). 1992 



DeMetrio et al. (1989) found mature female swordfish 

 as young as age 2, with most mature by age 3. How- 

 ever, Yabe et al. (1959) suggested that female sword- 

 fish in the North Pacific mature at age 5 or 6. This is 

 in agreement with our age-at-50%-maturity for females 

 (5.5 years). Although we found no information on 

 maturation of male swordfish from the Pacific, most 

 male swordfish in the eastern Mediterranean reach 

 maturity by age 2 (DeMetrio et al. 1989), again similar 

 to our findings off southeast Florida. 



The observed protracted spawning of swordfish off 

 southeast Florida, with peak activity during April 

 through July, agrees with reported spawning seasons 

 determined from temporal changes in the abundance 

 of larvae and juveniles. Taning (1955) reported that 

 spawning off Florida and elsewhere in the North Atlan- 

 tic occurs throughout the year, with peak larval abun- 

 dances during February through April. The temporal 

 distribution of larval abundance in the western North 

 Atlantic suggests that swordfish spavra during Decem- 

 ber through September, with a peak in April (Arata 

 1954, Markle 1974, Grail et al. 1983). Off the coast of 

 southern California, gonads of female swordfish are 

 inactive from late-August through mid-November 

 (Weber and Goldberg 1986). This period of inactivity 

 coincides with low mean oocyte diameters of sword- 

 fish in the western Atlantic (Fig. 4), suggesting that 

 swordfish in the eastern Pacific and western Atlantic 

 may have similar annual spawning seasons. 



Two histological features present in ovarian tissue— 

 hydrated oocytes and postovulatory follicles— provided 

 evidence that female swordfish spawn off the coast of 

 southeast Florida between the Florida Keys and Cape 

 Canaveral. The presence of hydrated oocytes indicates 

 an imminent spawn, certainly within 12h. Young post- 

 ovulatory follicles found in many female swordfish pro- 

 vide evidence that spawning occurred within 24 h of 



capture. Further, short-term stud- 

 ies of the movement of swordfish, 

 using acoustic tags, have shown 

 that fish that were likely mature 

 (70- 140 kg) remained in the same 

 general area (<90km from tag- 

 ging) for up to 5d during the 

 peak of the spawning season 

 (April) off Baja California (Carey 

 and Robison 1981). More exten- 

 sive movement occurred for a 

 70kg swordfish tracked for 2.5d 

 in November in the vicinity of 

 Cape Hatteras, North Carolina. 

 This fish traveled 240km in 67 h, 

 heading from cold continental 

 shelf waters off Cape Hatteras to 

 warmer Sargasso Sea waters. 

 The combination of this information on net random 

 movement of swordfish with our observed histological 

 evidence for recent or imminent spawning suggests 

 that spawning occurs in our sampling area. Addition- 

 ally, Grail et al. (1983) found major concentrations of 

 swordfish larvae and juveniles in the western Atlantic 

 in the waters near the Lesser Antilles, in the Yucatan 

 Straits, and in the Florida Straits, implying the pres- 

 ence of a large spawning population in these areas. 

 Changes in sex ratios as swordfish increase in size 

 apparently result from differences in grow^th between 

 the sexes and possibly from seasonal differences in 

 their distribution. Swordfish larger than ~230cm are 

 female because males have shorter life spans and 

 slower growth rates (Berkeley and Houde 1984, Wilson 

 1984). The dominance of males in our summer collec- 

 tions may be explained by seasonal differences in the 

 distribution of the sexes. Guitart-Manday (1964) found 

 a similar preponderance of males (72%) in samples from 

 the mainly summertime commercial fishery off Cuba. 

 Beckett (1974) reported that few males were taken in 

 the northern swordfish fisheries in waters <18°C, 

 whereas in more tropical latitudes, males account for 

 67-100% of the catch. Off southeast Florida, surface- 

 water temperatures remain >18°C throughout the 

 year, ranging from ~22°C in February to 29°C in 

 August (Atkinson et al. 1983). Our observed seasonal 

 changes in sex ratios of swordfish collected off 

 southeast Florida imply that whereas some males and 

 females are year-round inhabitants of these waters, 

 more females than males move north during the sum- 

 mer, which results in a dichotomous distribution that 

 becomes more acute the farther north the fish migrate. 

 At the northern extent of the range in the western 

 North Atlantic, off New England and the Canadian 

 maritimes, most, if not all, fish captured are females 

 (Lee 1942, Tibbo et al. 1961). 



