and. while the bony parts (vertebrae, operculae. fin 

 rays) show rings, these do not appear to be consis- 

 tently interpretable. Estimates from modal size fre- 

 quencies, vertebral rings, and tagging data suggest a 

 rapid growth rate with weights of 4, 15, 40, 70, and 

 1 10 kg after successive years for females. There are 

 insufficient data to determine whether the smaller 

 size obtained by males, relative to females, is due to 

 a slower growth rate , or to a considerably shorter life 

 span. The average size of 31 males for which detailed 

 morphometric data were available was 147.2 cm and 

 that of 134 females was 176.9 cm (fork length). 



TAGGING 



High recoveries (11 tags, 18.3%) have been made 

 of the 60 swordfish marked by modified harpoon 

 (Beckett, 1968). These fish were tagged while 

 swimming free at the surface. In contrast, of the 146 

 fish taken on longline and then released, only 2 

 (1.4%) have been recaptured. 



Migrations and Stock Identification 



The spawning data, as judged from the occurrence 

 of larvae, indicate considerable migration of sword- 

 fish between the northern feeding areas and southern 

 reproductive zones (Markle, 1974). However, the 

 separate nature of the actual areas where larvae have 

 been found (Virgin Islands, Windward Islands, 

 Windward Passage, Northwest Caribbean, Florida 

 Straits, and Western Gulf of Mexico) suggests the 



possibility of some stock separation between these 

 areas. 



In the north, the tagging data (Table 1) for the 13 

 fish recaptured suggests that swordfish return to the 

 same part of the summer feeding area in subsequent 

 years. No tagged fish have changed the general local- 

 ity either within, or between years, the maximum 

 displacement being 179 miles and the recovery posi- 

 tion for that fish is suspect. Furthermore, mor- 

 phometric data suggests some heterogeneity be- 

 tween the fish on Georges Bank (Fig. 1) and those 

 on the Grand Banks, during the summer. Additional 

 studies that were being undertaken on this matter, 

 particularly tagging, have been frustrated by the 

 mercury-inspired cessation of commercial long- 

 lining. 



ACKNOWLEDGMENTS 



Many people have worked in the Large Pelagic 

 Fish programme, and I particularly acknowledge S. 

 N. Tibbo. Programme Head, and my many compan- 

 ions on sea cruises. 



LITERATURE CITED 



BECKETT. J. S. 



I%8. A harpoon adapter for tagging large free-swimming fish 

 at the surface. J. Fish. Res. Board Can. 2.';:177-179. 

 FISH. M. P. 



1926. Swordfish eggs. Bull. N. Y. Zool. Soc. 29:206-207. 

 MARKLE. G. E. 



1974. Distribution of larval swordfish in the northwest Atlan- 

 tic Ocean. In Richard S. Shomura and Francis Williams 



Table 1. — Swordfish tag returns. 



105 



