632 



Fishery Bulletin 103(4) 



Table 10 



Life-status condition of 571 sharks at time of capture, by species, and per fishing gear, observed onboard commercial fishing ves- 

 sels in the Mediterranean Sea during 1998-2000. Gear abbreviations: SWO-LL = swordfish longline, SWO-LL A =American-type 

 swordfish longline, ABL-LL=albacore longline, DN=driftnet, BFT-LL=bluefin tuna longline. 



Good 



Fair 



Poor 



1958; Carey and Scharold, 1990; Nakano, 1994; Bigelow 

 et al., 1999). 



The abundance and widespread distribution of blue 

 sharks throughout the Mediterranean that we deter- 

 mined supports previous findings. However, our ob- 

 served catch rates were lower than those reported ear- 

 lier for the same areas (De Metrio et al., 1984; Filanti 

 et al., 1986; Buencuerpo et al., 1998; Di Natale, 1998; 

 Relini-Orsi et al., 1999; De Zio et al., 2000). Varia- 

 tion in sex ratio and size distribution between differ- 

 ent areas studied indicated sexual or size segregation, 

 or both. Spatial and temporal segregation of pelagic 

 sharks by sex and size was well documented by Stras- 

 burg (1958) and Nakano (1994) in the Pacific Ocean. 

 Further analysis regarding distribution by latitude- 

 longitude, time of year, and size classes of specimens 

 is needed to establish a possible blue shark migratory 

 pattern in the Mediterranean Sea. Pratt's estimates on 

 the sexual maturity of blue shark (215 cm TL for males, 

 257 cm TL for females) from the North Atlantic Ocean 

 (Pratt, 1979) indicate that in all areas studied in the 

 Mediterranean Sea, albacore and swordfish longline 

 fisheries generally capture immature to subadult speci- 

 mens and driftnets and American type swordfish long- 

 lines capture adults. Of all blue sharks captured in the 

 large pelagic fisheries of the Mediterranean during our 

 study, 91.1% were under 215 cm TL and 96.3% under 

 257 cm TL. This observation, which indicates that the 

 majority of Mediterranean blue sharks caught have not 

 reached maturity, is of concern and reinforces the need 

 for global assessments of this species. In the Atlantic 

 and Pacific Ocean results based on a considerable time 



series of data show a decrease in abundance (Cramer, 

 1996) and in average size (Holts et al., 1998) of blue 

 sharks. Because blue sharks are an incidental catch in 

 the large pelagic and highly migratory species fisheries 

 in the Mediterranean, standardizing catch rates is very 

 difficult. Average size may be a more sensitive indicator 

 of shark stock status than catch rates when there is a 

 long enough time-series of data. 



We found a much lower incidental catch of shortfin 

 mako than other authors have reported in the Medi- 

 terranean (Dai, 1997; Buencuerpo et al., 1998). This 

 species seems more abundant in the Atlantic Ocean 

 where in some areas it represents more than 10% of 

 total catches (Buencuerpo et al., 1998; Stone et al., 

 2001). The almost equal sex ratio reflects the findings 

 of Buencuerpo et al., (1998) and Moreno et al., (1992). 

 As with blue sharks, larger makos were observed in the 

 Levantine basin although in small numbers. Because 

 males mature at 195 cm TL (Compagno, 1984) and 

 females between 273 and 298 cm (Mollet et al., 2000), 

 98.4% of shortfin makos in our study were smaller than 

 the size of first maturity. The absence of a consistent 

 time series of abundance data did not allow us to es- 

 timate the trend in the status of the shortfin mako 

 population in the Mediterranean Sea. Cramer (1996) 

 outlined a steady decline in catch indices for this spe- 

 cies from 11.86 fish/1000 hooks in 1985, to 3.52 in 1996 

 for the U.S. commercial Atlantic longline fishery in the 

 Caribbean and the Gulf of Mexico. The Azorean fleet 

 mako landings decreased by almost 50% in numbers 

 from 1987 to 1994 (Castro et al., 1999). Together with 

 the low catch rates in the Mediterranean Sea, short- 



