FISHERY BULLETIN: VOL. 70, NO. 2 



white marlin again are concentrated in the west- 

 ern South Atlantic off Brazil and in the South 

 Equatorial Current. 



We hypothesize that there are no major mi- 

 grations of white marlin between the North and 

 South Atlantic Oceans because the areas of con- 

 centrations of white marlin in the two oceans 

 are generally separated by areas of low catch 

 rates for white marlin and because not a single 

 fish tagged in the North Atlantic has been re- 

 captured in the South Atlantic. The North and 

 South Atlantic groups of white marlin may be 

 separate populations; Kamimura and Honma 

 ( 1958a, b) believe that the closely related striped 

 marlin of the Pacific Ocean has separate popula- 

 tions in the northern and southern hemispheres. 



BLUE MARLIN 



Monthly distribution of catches of blue mar- 

 lin by Japanese longliners reveals two major 

 seasonal concentrations in the Atlantic Ocean 

 (Figure 7) . In the Caribbean Sea, Gulf of Mex- 

 ico, and the western North Atlantic Ocean south 

 of lat 35°N, blue marlin are most abundant in 

 the longline fishery from June through October. 

 In the western and central South Atlantic Ocean, 

 between lat 10° and lat 20 °S, blue marlin are 

 most abundant in February, March, and April. 

 Possible migratory routes between the two areas 

 are fished by the Japanese during all months of 

 the year, but longline catches have produced no 

 evidence that blue marlin move between the two 

 oceanic regions. There may be two populations 

 of blue marlin in the western Atlantic which are 

 relatively unavailable to the longline fishery at 

 certain seasons of the year, or there may be a 

 single population which is unavailable to the 

 fishery while the fish are migrating between the 

 two areas. We believe that the two widely sep- 

 arated concentrations of blue marlin represent 

 separate spawning populations. The evidence 

 suggests that blue marlin in the North Atlantic 

 spawn mainly from July through September and 

 those in the South Atlantic spawn in February 

 and March. It is unlikely that a single popula- 

 tion of blue marlin would spawn at two widely 

 separate locations at different times of the year. 

 Eschmeyer and Bullis (1968) examined four 



larvae of blue marlin from the western North 

 Atlantic captured in July and September, and 

 Gehringer (1957) reported three larvae from 

 the western North Atlantic and Gulf of Mexico 

 in spring and summer, which were later iden- 

 tified as blue marlin by Ueyanagi and Yabe 

 (1959). Caldwell (1962) reported on two post- 

 larvae of blue marlin captured off Jamaica in 

 September. Erdman (1968) concluded from his 

 studies of gonad development and sex ratio that 

 the peak spawning season for blue marlin oflF 

 Puerto Rico was in July and August. In the 

 South Atlantic, Bartlett and Haedrich (1968) 

 reported on 85 larvae of blue marlin captured 

 oflF the coast of Brazil in February and March. 

 The size range was from 4.9 to 32.0 mm. 



The blue marlin is apparently the only' bill- 

 fish in the Atlantic whose abundance has been 

 significantly affected by longline fishing. Wise 

 and Le Guen (1969) showed significant rates of 

 decline in relative apparent abundance of blue 

 marlin in the two areas of major concentrations 

 shown in Figure 7. They stated that these de- 

 clines were associated with the intensive fishing 

 for albacore and yellowfin tuna in the same 

 areas. Ueyanagi et al. (1970) also reported a 

 drastic decline in the apparent abundance of 

 blue marlin in the Atlantic with the level of 

 apparent abundance in 1965 only about one- 

 fourth of that of 1962. 



SUMMARY 



WHITE MARLIN 



1. Tag returns indicate that one group of 

 white marlin moves from the middle Atlantic 

 coast of the United States in summer to the north 

 coast of South America in winter. The route 

 appears to be initially offshore from the summer 

 grounds, then south to the wintering area. The 

 return is north in the vicinity of the Antilles and 

 the Bahamas, including the Yucatan Channel 

 and the Straits of Florida. 



2. Longline catches support the above hypoth- 

 esis but also indicate that a second group of 



* Recent unpublished data suggest that the abundance 

 of broadbill swordfish and white marlin in the Atlantic 

 may also have been reduced by longline fishing. 



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