the Yucatan Peninsula) in June (4.1 mo at liberty); 

 and off Fort Lauderdale. Florida, in May (4.0 mo at 

 liberty) (Appendix Table 7). The first two fish might 

 have been on their way to the northern Gulf of Mex- 

 ico, or, as the third could also have been, to the 

 Jacksonville-Cape Hatteras area. A sailfish released 

 off Palm Beach in January and recaptured off 

 Havana in May (3.3 mo at liberty) (Appendix Table 

 1) might well have been en route to the northern Gulf 

 of Mexico. 



Thus the majority (eight) of the 13 recorded sail- 

 fish migrations between temperate and tropical 

 waters were between the northern Gulf of Mexico 

 in the warmer season and the waters off southeast- 

 ern Florida and the north coast of Cuba in the 

 cooler season. Similar migrations have been re- 

 corded for tagged white and blue marlins (Mather, 

 Jones, and Beardsley, 1972: Mather, Mason, and 

 Clark, 1974), although several of these originated 

 off the northwestern Bahamas. There seems to be a 

 strong tendency for sailfish, as well as other bill- 

 fishes, to spend the warm-water season in the 

 northern Gulf of Mexico, and the season when the 

 waters there are cool, in the Straits of Florida and 

 adjacent waters. Gibbs (1957) showed the white 

 marlin distribution in the Gulf of Mexico was 

 closely related to the seasonal movements of the 

 75°F (23.9°C) isotherm. Since the range of the sail- 

 fish does not extend into waters as cool as that of 

 the white marlin (Ueyanagi et al., 1970) it seems 

 probable that the position of the 25°C isotherm 

 might control their distribution. 



Similar, but less frequent, seasonal changes of 

 habitat by tagged sailfish have been between the 

 Straits of Florida and the Virgin Islands in the cool 

 season and the Jacksonville-Cape Hatteras area in 

 the warm season (two northward migrations and 

 one southward); and between the latter area and the 

 Gulf of Mexico in the warm season, and waters 

 near northeastern South America in the cool season 

 (two southward migrations) (Fig. 2, Appendix Ta- 

 bles 1, 6, 7, 9). Like the more numerous seasonal 

 migrations between the Gulf of Mexico and the 

 Straits of Florida area, these migrations may be re- 

 lated to the seasonal temperature changes in the 

 summering areas. The data are insufficient to de- 

 termine whether different stocks occupy the two 

 summering areas (Gulf of Mexico. Jacksonville- 

 Cape Hatteras) or not. It seems highly probable, 

 however, that fish from these two summer habitats 

 mingle with each other in three wintering areas 

 — Straits of Florida. Virgin Islands, and off South 



America. Since the recovery of tags is probable in 

 only a few relatively small areas of intensive fish- 

 ing, the picture obtained from tag returns may be 

 misleading. It is quite likely that the seasonal 

 habitats of sailfish are considerably larger than is 

 indicated here. Possibly the wintering area is con- 

 tinuous from the Straits of Florida and the north- 

 western Bahamas to northeastern South America. 



In contrast to the long migrations recorded from 

 other areas where numerous sailfish have been 

 tagged, all seven returns from the 439 releases 

 off Venezuela have been local even though times 

 at liberty have ranged up to 54.8 mo (Table 2, 

 Appendix Table 8). This is a strong indication that 

 most of the sailfish there are of a local stock, or one 

 which does not enter other areas of intensive fish- 

 ing. Tag returns (Fig. 2) suggest, however, that sail- 

 fish from the northern Gulf of Mexico, the 

 Jacksonville-Cape Hatteras area, and off the north- 

 eastern coast of the Yucatan Peninsula may mingle 

 with those off Venezuela. 



The extremely low return rates for sailfish tagged 

 off Yucatan and in the northwestern Gulf of Mex- 

 ico (Table 2) suggest that these fish may also be of 

 stocks which do not often enter other areas of in- 

 tensive fishing. 



It is also surprising that, with 9,710 sailfish tagged 

 off southeastern Florida and 508 tagged off the 

 northwestern Bahamas, only two migrations (one in 

 each direction) between these areas have been re- 

 corded (Appendix Tables 1, 5). This small amount 

 of mixing again raises the possibility of separate 

 stocks. 



In view of the present low rate of return from 

 sailfish tagging, it seems especially important to 

 conduct genetic studies of sailfish in the respective 

 areas to identify the stocks or populations. Perhaps 

 the tagging results could assist in the selection of 

 sampling periods and areas when mixing of fish 

 from different areas is least probable. 



The numerous local movement records within the 

 Fort Pierce-Key West area (southeastern Florida) 

 are very difficult to analyze (Appendix Tables 

 2, 3, 4). More southward (32) than northward (16) 

 migrations were recorded, but this may only reflect 

 the fact that the majority of the tagging occurred in 

 the northernmost part of this area (Palm Beach- 

 Fort Pierce). Fishing effort from Palm Beach 

 southward to Key West is intense, whereas it is 

 relatively light north of Fort Pierce. Most of the 

 tagged sailfish which migrated northward in the 

 area were released in October-April and recaptured 



200 



