Buencuerpo et at: Pelagic sharks associated with the swordfish fishery 
673 
of maximum, median, and minimum sizes are pre- for this species were very low in relation to other 
sented in Figure 6, A and B. species, in some months almost negligible (Table 7). 
In the longline fishery, sex ratio by sector was close 
Blue shark to 1 male:0.25 females, except in sector 3 where it 
was almost equal (1 male:0.92 females); gillnet sex 
Blue sharks are often discarded at sea because they ratio (1 male:2.45 females) was inverse to that ob- 
are not commercially valuable in the Spanish mar- served for longlines in the same sector. Monthly data 
ket; real catch rates are biased by this factor, espe- were not sufficient to be analyzed and therefore were 
daily in the more distant sectors where the tendency grouped by quarter, i.e. July-September 1991, Octo- 
is to try to improve long trips with more valuable ber-December 1991, January-March 1992, and 
species, i.e. with swordfish and shortfin mako shark. April-June 1992. Because of the effect of discarded 
Therefore, sectors 1 and 2 had lower catch rates, fish at sea and inappropriate sex sampling, we were 
based on landings, than sectors 3, 4, and 5 (Table 5). unable to make significant assertations about sex 
Longline catch rates by month (Table 6) ranged from ratio variability. 
6 to 52 fish/1000 hooks, except for an extremely high The distribution of overall length frequency is pre- 
rate in April (182 fish/1 000 hooks). Gillnet catch rates sented in Figure 7A. In longline landings, modal 
Table 8 
Biometric relations of standard length ( SL ) with fork length ( FL ), total length (TL), and upper caudal lobe length (UCL); and of 
fork length with total length by sex for Isurus oxyrinchus, Prionace glauca, and Alopias superciliosus, and both sexes combined 
for Alopias vulpinus and Sphyrna zygaena. 
Females 
Males 
Total 
Isurus oxyrinchus 
FL = 1.086 SL + 1.630 
FL = 1.086 SL + 1.409 
FL = 1.086 SL + 1.515 
r 2 = 0.993 n = 852 
r 2 = 0.993 77 = 911 
t- 2 = 0.993 77 = 1,763 
TL = 0.817 SL + 0.400 
TL = 1.209 SL + 0.435 
TL = 1.207 SL + 0.971 
r 2 = 0.986 n = 852 
r 2 = 0.983 77 = 681 
t- 2 = 0.985 77 = 1,533 
UCL = 3.693 SL + 13.094 
UCL = 3.795 SL + 10.452 
UCL = 3.758 SL + 11.640 
r 2 = 0.874 n = 507 
r 2 = 0.898 77 = 477 
r 2 = 0.903 7? = 1,054 
TL = 1.106 FL + 0.052 
TL = 1.111 FL - 0.870 
TL = 1.108 FL-0.480 
r 2 = 0.985 n = 853 
r 2 = 0.984 77 = 911 
T- 2 = 0.984 77 = 1,746 
Prionace glauca 
FL = 1.076 SL + 1.862 
FL = 1.080 SL + 1.552 
FL = 1.079 SL + 1.668 
r 2 = 0.993 n = 1,043 
t- 2 = 0.997 77 = 1,276 
r 2 = 0.996 77 = 2,319 
TL = 1.249 SL + 7.476 
TL = 1.272 SL + 4.466 
TL = 1.262 SL + 5.746 
r 2 = 0.986 n = 1,043 
r 2 = 0.993 77 = 1,272 
r 2 = 0.990 77 = 2,315 
UCL = 0.219 SL + 4.861 
UCL = 0.316 SL + 2.191 
UCL = 0.306 SL + 3.288 
r 2 = 0.903 n = 1,038 
r 2 = 0.948 77 = 1,264 
r 2 = 0.929 77 = 2,302 
TL = 1.158 FL + 5.678 
TL = 1.117 FL + 2.958 
TL = 1.167 FL+ 4.133 
r 2 = 0.988 n = 1,043 
t- 2 = 0.992 77 = 1,272 
r 2 = 0.990 77 = 2,315 
Alopias superciliosus 
FL = 1.075 SL + 3.346 
FL = 1.081 SL + 3.324 
FL = 1.073 SL + 4.150 
r 2 = 0.987 n = 90 
r 2 = 0.980 77 = 76 
T- 2 = 0.986 77 = 166 
TL = 1.939 SL - 11.990 
TL = 1.897 SL - 7.359 
TL = 1.937 SL -12.630 
r 2 = 0.976 77 = 77 
r 2 = 0.946 77 = 70 
7-2 = 0.970 7? = 147 
UCL = 0.967 SL -9.588 
UCL = 0.922 SL -5.353 
UCL = 0.966 SL - 10.908 
r 2 = 0.952 77 = 75 
T- 2 = 0.869 77 = 71 
7-2 = 0.932 77 = 146 
TL = 1.775 FL - 13.007 
TL = 1.722 FL - 7.295 
TL = 1.773 FL- 14.456 
t- 2 = 0.956 77 = 77 
r 2 = 0.923 77 = 70 
r 2 = 0.949 77 = 147 
Alopias vulpinus 
Sphyrna zygaena 
Relation r 2 n 
Relation r 2 
n 
FL = 1.118 SL - 2.29 0.989 22 
FL = 0.845 SL + 1.077 0.998 
56 
TL = 1.930 SL + 9.331 0.956 22 
TL = 1.322 SL + 8.397 0.994 
56 
UCL = 0.926 SL + 25.670 0.949 22 
UCL = 0.329 SL + 8.799 0.975 
55 
TL = 1.687 FL + 20.483 0.932 22 
TL = 1.225 FL + 7.528 0.994 
56 
