810 



Fishery Bulletin 90(4). 1992 



20 mi 



Figure I 



Areal extent of sampling locations (shaded area) off southeast Florida during June 

 1977-November 1980. Triangles indicate where female swordfish Xiphias glndius were 

 found with histological evidence for recent (postovulatory follicles) or imminent (hydrated 

 oocytes) spawning (see "Methods and materials"). 



Ages for the swordfish that com- 

 prise this data set were deter- 

 mined by Berkeley and Houde 

 (1984), who counted unvalidated 

 age marks found on thin-sections 

 of the second anal-fin spine. 



Temporal differences in mean 

 oocyte diameters were used to 

 define spawning season. To de- 

 termine mean oocyte diameter 

 for each individual, 100 oocytes 

 in a common lamella were mea- 

 sured with an ocular micrometer. 

 Mean oocyte diameters were cal- 

 culated for all collections in a 

 given month and plotted to ex- 

 amine monthly changes. The dis- 

 tribution of oocyte diameters was 

 also examined within individuals 

 to determine whether swordfish 

 undergo multiple spawns or a 

 single spawn each year. 



We used the distribution of 

 swordfish captured in near-term 

 spawning condition to delimit 

 their spawning grounds off south- 

 east Florida. Histological fea- 

 tures indicative of recent or im- 

 minent spawning included post- 

 ovulatory follicles and hydrated 

 oocytes (DeMartini and Fountain 

 1981, Hunter and Macewicz 1985). 

 For a variety of fishes, it has 

 been found that oocytes hydrate 

 during the late-afternoon or eve- 

 ning just prior to spawning {Ser- 

 rifus politics, DeMartini and Foun- 

 tain 1981; Engraulis mordax, 

 Hunter and Macewicz 1985; Cyno 

 scion nebulosus, Brown-Peterson 

 et al. 1988; Sciaenops ocellatus, 

 Fitzhugh et al. 1988). Postovula- 

 tory follicles are identifiable only 

 for a short time. Following spawn- 

 ing, they are rapidly absorbed 

 (within 6h for Callionymus enne- 

 actis, Takita et al. 1983) and 

 quickly become indistinguishable 

 from other atretic structures 

 (within 2d in Engraulis mordax, 

 Hunter and Macewicz 1985). 



Batch fecundity was estimated 

 gravimetrically from counts of 

 ova >750Mm diameter in a 2-3 g 

 portion from the midsection of 

 each preserved ovary (n 7). 



