Istiophorus platypterus. The data for this return 

 support the opinion of Mather et al. (1972) that the 

 concentrations of blue marlin in the western North 

 Atlantic from June through October, and in the 

 western and central South Atlantic in February, 

 March, and April, represent separate populations. 

 This return also gives the first available indication 

 of the growth rate of Atlantic blue marlin. The 

 fish's weight when released was estimated at 200 

 pounds (90 kg), and it weighed 163 kg (eviscerated) 

 when recaptured after 30 mo at liberty. Since esti- 

 mates of the weight of fish when tagged have usu- 

 ally proved to be high, it seems probable that this 

 fish doubled its weight in two and a half years. The 

 other return was from a 165 pound (75 kg) blue mar- 

 lin recaptured at Cape Hatteras, North Carolina, in 

 August 1970. Unfortunately, the serial number on 

 the streamer was illegible and the dart, which also 

 carried the serial number, was not returned. To our 

 knowledge, only 14 blue marlin in this size range or 

 smaller had been marked prior to this recapture 

 with the type tag returned from this fish. Six of 

 these were released off the Virgin Islands, June- 

 November 1969. and 8 off the northwestern 



Bahamas and southeastern Florida, April- 

 December 1969. It is highly probable that the recap- 

 tured fish was one of these, but there is also a pos- 

 sibility that the sportsman who tagged it neglected 

 to report the data. 



Tag return rates for blue marlin in recent years 

 have been about 1%. This low rate and the small 

 number (usually less than 100) tagged each year 

 have made the accumulation of tag return data for 

 this species extremely slow. Future tagging efforts 

 would be most effective if concentrated on marking 

 as many small individuals as possible. 



SUMMARY 



White Marlin 



A. Fish which summer between Cape Hatteras 

 and Cape Cod. 



1. These fish move offshore, mainly in east- 

 erly to southerly directions, in late summer 

 and early fall. 



2. Most of these fish winter off northern 

 South America and some may remain there 



40° 



• RELEASE 

 O RECAPTURE 



LESS THAN 1 YEAR 



AT LIBERTY { MORE THAN 1 YEAR 



UNCERTAIN 



40° 



Figure 6. — Locations of releases and recaptures for blue marlin tagged in the western 

 North Atlantic Ocean. The months and years of release and recapture are shown in that 

 order for each return. 



220 



