Table 4.—Estimated age composition of yellowfin tuna caught by the 
American purse seine fleet in the eastern tropical Atlantic. 
Approximate 
Estimated catch (numbers) by year 
length (cm)| 969 1969 1970 1971 1972 1973 1974 
35-51 29,900 | 169,100 
52-91 230,300 | 116,900 
92-125 54,200 | 339,600 
126-149 16,400 | 142,900 
150-169 38,600 | 41,100 
170+ 19,400 3,200 
358,900 | 643,700}1,110,800 | 460,100 | 1,414,600] 245,900 
1974 
PERCENT FREQUENCY 
1973 
~ 40 50 60 70 30 40 50 60 70 
FORK LENGTH (cm) 
Figure 3.—Estimated length composition of skipjack tuna caught by 
American seiners in the eastern tropical Atlantic, 1968-74. (Solid 
line — stratified procedure; dashed line — unstratified procedure.) 
907,500 | 186,600 
63,000 
77,700 
25,700 7,000 
368,300} 25,200 46,700 
763,600} 122,000 | 157,800 
81,100 218,500} 82,700 99,500 
16,300 46,600} 15,300 99,800 
15,300 700 13,400 
7,000 2,300 
417,200 
American catch was made in the Gulf of Guinea and only 
about 3 to 21% of the skipjack tuna was caught in area 
52. Since the discovery in 1971, as much as 98% of the an- 
nual American catch of skipjack has been taken from 
area 52. 
Bigeye Tuna 
Bigeye tuna are not often available to the surface 
fisheries (purse seine and pole-and-line) of the eastern 
tropical Atlantic. This species is sometimes confused 
with yellowfin tuna and catches may have been included 
with yellowfin tuna catches, but the amount is probably 
small. The American fleet reported bigeye tuna catches 
only in 1968 and 1971-74. A few length-frequency 
samples were collected in those years (Table 6). Because 
the samples were few, estimates of the length com- 
position of the catch were based on all samples com- 
bined without stratification, i.e., all catches and samples 
pooled and one estimate calculated for each year (Ap- 
pendix Table 17): 
About four major modal groups (39 to 51 cm, 52 to 73 
cm, 74 to 105 cm, and 106 to 131 cm) can be identified in 
the length-frequency distributions (Fig. 4). These groups 
apparently represent age groups of 1 to 4 yr, based on 
Table 5.—Estimated age composition of skipjack tuna caught by the 
American purse seine fleet in the eastern tropical Atlantic. 
Approximate 
Estimated catch (numbers) by year 
lenge taken) bi <igg8 1969 | 1970 1971 1972 1973 
531,000} 4,268,700) 6,413,700| 7,290,200} 12,754,800} 9,327,500 
409,700 }1,137,300 
486 ,000} 2,069,200 
1,212,500 |1,668,300}4,754,700}8,482,900| 7,411,800) 12,798,100}10,550,300 
