failed to collect a single larva of this 

 species (Judrez 1974b). Three juveniles 

 21-33 mm long collected off Maryland 

 (37°42'N latitude, 73°10'W longitude) 

 and New Jersey (38°45'N latitude, 

 71''00'W longitude) July 27-28, 1959, 

 have been identified as bluefin tuna by 

 Watson (Watson and Mather 1 96 1 ) and 

 this identification has been verified 

 (T.C. Potthoff, personal communica- 

 tion). These records are the most north- 

 erly in the western Atlantic for small 

 juvenile bluefin. They are of special 

 interest because they are from the area 

 where medium-sized bluefin may 

 spawn (Matiier l974,Baglin 1976). The 

 spawning habits of these fish in the 

 western Atlantic are little known, but 

 they do not occur in numbers anywhere 

 near the known spawning areas of the 

 large bluefin (Madier 1963a; also see 

 Section IV). 



Examinations of gonads suggest 

 that the spawning grounds of the blue- 

 fin tuna in the western North Atlantic 

 may be much more extensive than is 

 indicated by the distribution of catches 

 of larvae, or even of juveniles (Mather 

 1974, Baglin 1976). 



Rivas ( 1 954) examined the gonads 

 of 95 large ( 1 99.7-255.0 cm long) blue- 

 fin tuna caught near Bimini, Bahamas, 

 all in the month of May, but in three 

 different years, 1952, 1953 and 1954. 

 He classified the specimens, by the color 

 and consistency of the gonads, the na- 

 ture of the ovarian eggs, and the amount 



of milt present, as recently spent, partly 

 spent, or ripe. 



All of the 29 males examined were 

 classed as recently spent. He also con- 

 sidered that 6 1 of the 66 females exam- 

 ined were recently spent, but one was 

 j udged to be partly spent, and four were 

 considered ripe. 



The smaller eggs of ripe females 

 were non-spherical, opaque and mea- 

 sured 0.4 to 0.7 mm in diameter, with a 

 mode at about 0.6 mm. The larger eggs 

 were spherical, translucent, yolk-filled, 

 and measured 0.7 to 1.1 mm in diam- 

 eter, with a mode at about 0.9 mm. 

 Rivas ( 1 954) offered two possible ex- 

 planations for the small number of ripe 

 individuals (about 4%) found in com- 

 parison with the larger number (about 

 96%) of spent individuals. Since the 

 fish which are observed in the area are 

 nearly always travelling northward, it 

 was possible that they had spawned in 

 an area south, or southwest, of the fish- 

 ing area near Bimini and were caught 

 when spawning had been nearly com- 

 pleted. He assumed that they had mi- 

 grated to this area through the Straits of 

 Florida, passing close to Havana, Cuba, 

 and the western edge of Cay Sal Bank. 

 The other possible explanation which 

 Rivas offered was that the rod and reel 

 fishing method used at Bimini selected 

 spent rather than ripe fish. He quoted 

 previous authors on the reluctance of 

 spawning fish to feed. 



During cruise 57-5 of the Bureau 

 of Commercial Fisheries M/V "Dela- 



ware", R. H. Gibbs and B. B. Collette, 

 then of Woods Hole Oceanographic 

 Institution, macroscopically examined 

 the gonads of 48 bluefin tuna caught 

 during the period June 8-14, 1957, in 

 the area between latitudes 37°30'N and 

 40°30'N and longitudes 66°W and 

 70°W. Their observations were repro- 

 duced by Baglin (1976). Two age-3 

 (95-105 cm) individuals were consid- 

 ered immature. The testes of one male 

 of age 4(121 cm) contained abundant 

 milt. Two other males and two females 

 of this age group were classed as im- 

 mature, but the ovaries of another age- 

 4 female were "much vasculated," a 

 sign of ripening. Milt was squeezed 

 from the testes of a 5-year-oid (140 

 cm) male. The ovaries of a female of 

 the same age-size group were preserved 

 for laboratory examination, presumably 

 because of signs of maturity. Six males 

 and six females, probably 6 years old 

 ( 143.5-1 57.2 cm), were examined. The 

 testes of all of the males contained abun- 

 dant sperm; those of one individual 

 were much enlarged, and another was 

 classified as ripe. One female was 

 classed as "near ripe." The ovaries of 

 another contained eggs which seemed 

 to be nearly ripe, but were not loose. 

 Those of two others were well devel- 

 oped and loose, indicating imminent 

 spawning. The ovaries of the last two 

 females of this group contained no eggs, 

 and were believed to be spent. 



These observations, and less nu- 

 merous ones from later catches of the 



Table 24. Number of surface tows and number of larvae collected 25 nautical miles (4.0 km) from the Miami harbor 

 entrance (Station 1) (1969-1971 and 1975) and additional stations (2-5) completing a n-ansect of the Straits of Florida from 

 Miami to Bimini, Bahamas, in 1975'. Data are from Richards (1976). 



82 



