23°50'N latitude, 88°40'W longitude 

 on May 17, 1972 (Judiez 1972). 

 Considerable quantities of these larvae 

 were also collected near this location in 

 the subsequent surveys of April to May 

 1973 and May to June 1974. 



T.C. Potthoff (personal communi- 

 cation) reported the collection of one 

 larval T. thynnus tliyrmns 5.5 mm SL 

 June 29, 1969, and four larvae 3.6-4.2 

 mm SL on July 6, 1 969, in the northern 

 Gulf of Mexico near 29°N latitude and 

 87°W longitude. Thus, these were cap- 

 tured near the northeastern boundary 

 of the area where Juarez (1974) and 

 Montolio and Ju^ez (1977) took most 

 of their specimens, but the dates of 

 capture extend the time of occurrence 

 of the bluefin tuna larvae in the Gulf of 

 Mexico into July. 



Richards (1977) provided addi- 

 tional data on occurrences of bluefin 

 tuna larvae in the Gulf of Mexico. Nine- 

 teen larvae ranging from 3.9 to 7.4 mm 

 SL were collected near 27°N latitude, 

 96° W longitude, on May 6, 1975, and 

 May 30- June 6, 1976. 



Another important series of col- 

 lections of bluefin larvae was made off 

 Miami, Florida, witli surface tows (fi-om 

 1 969 to 1 97 1 ) and on a transect from 

 Miami to Bimini, Bahamas, with sur- 

 face tows and oblique tows to 200 m 

 depth (in 1975) (Richards 1976). The 

 cumulative numbers of surface tows 

 and captures of larval bluefin tuna are 

 listed by half-month periods in Table 

 24. In total, 93 tows were made, and 

 1 64 identifiable bluefin tuna larvae of 

 3.3 to 7.2 mm SL were collected, an 

 average of 1 .8 larvae per tow. The tows 

 extended over a period from April 2 to 

 July 8, but bluefin larvae were taken 

 between April 22 and June 26 only. 

 The number of larvae per tow was only 

 0. 1 in the second haH of April, but rose 

 to 1.8 to 3.5 in the half month periods 

 of May and June, with maxima in tlie 

 first half of May and the last half of 

 June. 



During the transects in 1975, 39 

 larvae 3.4-7.3 mm SL were collected 

 in 61 surface tows at five stations, and 

 23 were collected in 47 oblique tows at 



35" - 



30" - 



25" - 



20" - 



15 



100* 



90' 



80« 



Figure 68. Bluefin tuna larvae sampled in the Gulf of Mexico. 



four stations (oblique tows at station 

 number 1 near the Miami harbor en- 

 trance buoy were omitted because the 

 depth of the water was insufficient). 

 The catch rates in numbers of larvae 

 per tow (both types combined) were 

 maximum, 0.8 and 0.6, at stations 2 

 and 3. Lower catch rates, 0.1 and 0.2, 

 were obtained at stations 1 and 4, and 

 no larvae at all were caught at station 5 

 on the Bahamas side of the Straits. This 

 distribution is rather surprising, as large 

 bluefin tuna are observed and caught in 

 considerable numbers along the edge 

 of the Great Bahama Bank near Bimini 

 in May and June but are a rarity on the 

 Florida side (Rivas 1954, Mather 

 1963a). A single larva (8 mm SL) col- 

 lected off St. Augustine, northeastern 

 Florida, (Figure 67) in May 1 968 (T.C. 

 Potthoff, personal communication) 

 completes our knowledge of the distri- 

 bution of bluefin tuna larvae in the 

 western North Atlantic system. 



The known range of small juve- 

 nile (12-120 mm SL) bluefin tuna in- 

 cludes much of that covered by the 

 larvae, but extends considerably far- 

 ther north (Figure 67). Rivas (1954) 

 collected a 45 mm SL juvenile off Mi- 

 ami on June 9, 1953. Potthoff and 

 Richards (1970) identified 40 juvenile 

 bluefin 22-118 mm long which had 

 been regurgitated by tems during a tem- 

 banding operation at the Dry Tortugas, 

 Florida, in June and the first half of 

 July 1960-1967. None were found in 

 May, although juveniles of other 

 scombrids were collected. No 

 scombrids less than 20 mm long were 

 collected in this manner. Twenty addi- 

 tional juvenile bluefin in the same gen- 

 eral size range and season have been 

 obtained from tems at the Dry Tortugas 

 subsequent to the 1970 publication 

 (T.C. Potthoff, personal communica- 

 tion). T.C. Potthoff (personal commu- 

 nication) also informed us of five juve- 

 nile bluefin 22-33 mm long collected 

 in the Gulf of Mexico in late May and 

 early June, and four others, 16-21 mm 

 long collected off the Carolinas in May. 

 A most surprising record, also provided 

 by Potthoff was of a 17.1 mm SL 

 juvenile collected off Mobile, Alabama, 

 on August 19, 1954. This specimen 

 must have been spawned long after 

 adult bluefin have usually left the Gulf, 

 and also in a month when the extensive 

 Cuban ichthyoplankton survey in 1973 



