Buencuerpo et a !.: Pelagic sharks associated with the swordfish fishery 
681 
compared with swordfish, were similar to proportions 
calculated by Garces and Rey (1983) for the north- 
eastern Atlantic and Mediterranean Sea but were 
greater than the estimates of Rey and Alot (1984) 
for the western Mediterranean Sea and those of 
Mejuto 2 for the northeastern Atlantic just immedi- 
ately north of the study area. Monthly variation in 
the longline catch rate in this study was different 
from that found off the northwestern Spanish coast 
by Mejuto and Garces 1 and Mejuto 2 , although it co- 
incides with the increased trend observed during the 
last few months of the year. Monthly catch rate varia- 
tion did not agree with results obtained on the other 
side of the Atlantic Ocean off the northwestern Cu- 
ban coast (Guitart, 1975). Shortfin mako shark and 
swordfish catch rates followed a similar decreasing 
trend from fall to March; in April the catch rate for 
shortfin mako sharks increased and that for sword- 
fish dropped (Fig. 10), thus complementing each 
other. 
Sex ratio (1 male:0.9 females) is different from that 
observed by Mejuto and Garces 1 and Mejuto 2 in the 
northeastern Atlantic above 40°N, where males were 
more abundant (approx. 1 male:0.4 females). The 
increasing presence of males northwards (up to 1 
male:0.6 females in sector 4) correlates with results 
observed by Mejuto and Garces 1 and Mejuto 2 and 
may suggest sexual segregation to the north. For the 
same area of the present study, Munoz-Chapuli 
(1984) observed a lower proportion of females (1 
male:0.35 females) than we did, and although the 
sample size was small in that study (n=113), there 
was a similar trend in the increasing number of males 
northwards. The overall sex ratio observed in this 
study agrees with results presented by Moreno and 
Moron ( 1992b) from August 1983 to August 1985 for 
the same fleet operating in the same area. Mejuto 2 
reported a trend of increase in percentage of males 
with increasing size (for size range 105-260 cm FL). 
This trend was not found in our study (Fig. 11). 
The length-frequency distribution of the two fish- 
eries was different from that found by Mejuto and 
Garces 1 and Mejuto 2 for the area immediately north. 
It was also different from the one presented for the 
east coast of the United States (Pratt and Casey, 
1983). In our study, modal values were always lower 
than those presented by the above-mentioned au- 
thors. Following the age structure proposed by Pratt 
and Casey ( 1983), we estimated that most of the fish 
in this study belonged to age class 1 and 2 for both 
sexes. The largest size of females corresponded to 
age class 5 (sector 3), and the largest size of males to 
[mj 
8 
O 5 
s 
CO 
Jul 91 Aug 91 Sep 91 Oct 91 Nov 91 Dec 91 Jan 92 Feb 92 Mar 92 Apr 92 May 92 Jun 92 Jui 92 
tl.oxyrinchus 1 .l.Xgladius 9 P.glauca 
Figure 10 
Comparison of longline catch rates (number of fish/1000 hooks) of the shortfin mako shark and swordfish (left “y” axis) and of the 
blue shark (right “y” axis) by month. 
