630 



Fishery Bulletin 103(4) 



40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 



Total Length (cm) 



Shortfm mako (Isurus oxyrinchus) 



n=257 



B,,« n 



40 60 80 100 120 140 160 180 200 220 240 260 280 300 

 Total Length (cm) 



50 100 150 200 250 300 350 400 450 500 550 



Total length (cm) 



Figure 4 



Length-frequency distribution (in percentage by 5-cm size classes) 

 for Prionace glauca, Isurus oxyrinchus, and Alopias vulpinus sampled 

 in the Mediterranean Sea during 1998-2000. 



of the highest in the world, rarely dropping 

 below 30% of the total catch in numbers 

 of fish (Amorim et al., 1998; Buencuerpo 

 et al., 1998; Hazin et al., 1998; Marin et 

 al., 1998). The higher incidence of sharks 

 in the Alboran Sea could also be due to 

 the higher trophic potential of the western 

 Mediterranean compared to the eastern 

 part. The discrepancies in observed at-sea 

 and at-landing data, especially in the west- 

 ern Mediterranean Sea catch composition, 

 could be mainly due to the discarding of 

 "other species." In addition, the discarding 

 of undersize target species, such as sword- 

 fish and tunas, could be another reason for 

 the discrepancies observed. It is reasonable 

 that observers at landing sites were not 

 able to record exactly the entire nonshark 

 discards at sea from the information that 

 fishermen provided; thus shark landings 

 do not always reflect actual percentage of 

 catch composition caught at sea. 



The shark catch rates obtained in our 

 study were lower than those reported in 

 previous studies for various areas of the 

 Mediterranean Sea (Table 11) probably be- 

 cause of the fishing pressure throughout 

 the years. 



A comparison of the shark catch rates in 

 the Mediterranean and Atlantic indicated 

 that the catch rates are generally lower 

 throughout the Mediterranean (Table 11). 

 Possible reasons could be either the lower 

 productivity of the Mediterranean Sea, or, 

 as alluded to above, lower availability of 

 sharks in the Mediterranean due to re- 

 gional depletion from historical fishing, or 

 both. The configuration and effectiveness 

 of fishing gears used could be another rea- 

 son for the higher CPUE in the Atlantic 

 Ocean. Hazin et al. (1998) and Kotas et 

 al. 2 reported an increase in use of wire 

 snoods in Atlantic swordfish fisheries to 

 retain more sharks for the growing market 

 for shark fins. 



Monthly analysis of catches indicated 

 that maximum catch rates occur during 

 late spring and summer (May-August) in 

 the swordfish longline (SWO-LL) fishery, 

 and in June in the driftnet fishery. Month- 

 ly variations in catch rates were found also 

 by Buencuerpo et al. (1998), who reported 

 peaks of shark catch in April and Septem- 



Kotas. J. E., S. dos Santos, V. G. de Azevedo. 

 J. H. de Lima, J. D. Neto, and C. F. Lin. 

 2000. Observations on shark by-catch in the 

 monofilament longline fishery off southern 

 Brazil and the National ban on finning, 8 p. 

 IBAMA-REVIZEE research. [Copyright: www. 

 wildaid.org.l 



