Buencuerpo et a I.: Pelagic sharks associated with the swordfish fishery 
677 
250 
275 
Fork length (cm) 
Figure 7 
(A) Total length-frequency distribution of blue shark from longline and gillnet landings from all sectors from July 1991 to July 
1992. (B) Size range variation of blue shark females landed by longlines and gill net (5GN) by sector from July 1991 to July 1992. 
(C) Size range variation of blue shark males landed by longlines and gill net (5GN) by sector from July 1991 to July 1992. 
fall to winter, dropping during spring. A maximun 
catch rate was reached in July 1991 (Table 6). In 
gillnet fishing, catch rates were highest during sum- 
mer months, with a maximum in July 1992 (Table 7). 
The sex ratio found in longline fishing was fairly 
balanced, 1 male to 1.1 females in sector 2 to 1 to 
0.93 females in sector 3. Females were more abun- 
dant than males in gillnet fishing (1 male: 1.43 fe- 
males). The distribution of sex ratio by sector was 
not significantly different (% 2 =9.14; df=5; P>0.1). The 
distribution of sex ratio varied significantly by month 
(/ 2 =38.7; df=ll; P<0.001). In longline fishing there 
were more males than females (1 male:0.66-0.69 fe- 
males), except in February and March when the ra- 
tio was 1 male: 1.45 females, and in September, when 
the proportion of females rose dramatically to 1 male:6. 1 
females. Gillnet fishing reflected a similar proportion 
during the same month (1 male: 13.21 females). 
The frequency distribution by size of fish from 
longline landings was quite similar for males and 
females (Fig. 8). Modal length for all sectors and 
months was near to 285 cm TL, the mean size ap- 
proximately 280 cm TL. Minimum size was 180 cm 
TL for females, 195 cm TL for males. Maximum size 
was 40 cm greater for females (430 cm TL) than for 
males (390 cm TL). 
The frequency distribution by size of fish from 
gillnet landings differed by sex (Fig. 9), with two 
modes for males (290 and 330 cm TL) and for females 
(395 and 410 cm TL). 
The size range of fish by sector for longline land- 
ings was greater for females (183-432 cm TL) than 
for males (195-391 cm TL). Minimum sizes were 
found in sector 2 for both sexes, whereas the maxi- 
mum for males was recorded in sector 3 and for fe- 
males in sector 5. In gillnet landings, females ranged 
from 236 to 446 cm TL, with a mean size of 352 cm 
TL, 45 cm larger than the mean size of males (307 
cm TL). As in longline landings, males had a smaller 
size range (246-373 cm TL). The length mode for fe- 
males was 80 cm larger than for males (410 cm TL 
compared with 330 cm TL). 
The size variation over time was not outstanding 
for males in either fishery, but there was a marked 
presence of large females during July-September in 
gillnet landings (288-446 cm TL) corroborated by 
longline landings in the same period (230-432 cm 
TL). The period of January to March was when the 
greatest number of fish were recorded ( 128 ) with the 
smallest size range ( 183-360 cm TL). Only one preg- 
nant female (385 cm TL), with one pup, was recorded 
in gillnet landings in September 1991. 
