620 



Abstract — Large pelagic sharks are 

 caught incidentally in the swordfish 

 and tuna fisheries of the Mediterra- 

 nean Sea. In our study, twelve shark 

 species were documented as bycatch 

 over three years from 1998 to 2000. 

 Blue shark (Prionace glauca) was 

 the predominant species in all gears 

 and areas examined. Shortfin mako 

 llsurus oxyrinchus), common thresher 

 shark tAlopias vulpinus), and tope 

 shark (Galeorhinus galeus) were the 

 next most abundant shark species — 

 found in more than half of the areas 

 sampled. Catch composition varied 

 both in the areas and gears investi- 

 gated. Sharks represented 34.3% in 

 weight of total catches sampled in the 

 Alboran Sea and 0.9% in the Straits 

 of Sicily. Higher shark catches were 

 observed in the swordfish longline 

 fishery, where a nominal CPUE value 

 reached 3.8 sharks/1000 hooks in the 

 Alboran Sea. Size distribution by fish- 

 ing gear varied significantly. Alba- 

 core longline catches consisted mainly 

 of juveniles, whereas subadult and 

 adult specimens were more frequent 

 in the swordfish longline and drift- 

 net fishery. The percentage of sharks 

 brought onboard alive was exception- 

 ally high; only 5.1% of the specimens 

 died. Few discards (seven blue shark I 

 were recorded in the Greek longline 

 fleet during onboard sampling in the 

 Aegean Sea. 



Incidental catch and estimated discards 



of pelagic sharks from the swordfish 



and tuna fisheries in the Mediterranean Sea 



Persefoni Megalofonou 



Constantinos Yannopoulos 



Dimitrios Damalas 



Department of Biology 



Section of Zoology-Marine Biology 



University of Athens 



Panepistimiopolis, llissia 



Athens 15784, Greece 



E-mail address (for P. Megalofonou) Pmegaloa biol uoa gr 



Gregorio De Metrio 



Michele Deflorio 



Department of Animal Health and Welfare 



Faculty of Veterinary Medicine 



University of Ban 



Str. Prov. Per Casamassima 



70010, Valenzano Ban, Italy 



Jose M. de la Serna 



David Macias 



Instituto Espanol de Oceanografia 



Malaga, Apartado 285 



29640 Fuengirola, Malaga, Spain 



Manuscript submitted 18 August 2003 

 to the Scientific Editor's Office. 



Manuscript approved for publication 

 8 April 2005 by the Scientific Editor. 



Fish. Bull. 103:620-634(2005). 



The effect of fishing on shark stocks 

 has become the focus of considerable 

 international concern. The fishery- 

 induced depletion of stocks is made 

 worse by the slow growth, late matu- 

 rity, and low fecundity of sharks, all 

 of which make them extremely vulner- 

 able even to modest levels of fishing. 

 Although no pelagic shark-directed 

 fishery exists in the Mediterranean 

 Sea, other pelagic fisheries may be 

 a great threat, because species with 

 higher production rates, such as 

 swordfish and tuna, continue to sup- 

 port the fishery while species with 

 lower rebound potential are driven to 

 stock collapse or extirpation (Musick 

 et al., 2000). In recent years sharks, 

 which were once considered bycatch 

 (and discarded), have become a target 

 species of the Spanish swordfish fleet 

 because highly restrictive measures 

 regulating swordfish catch have been 

 established in the Atlantic Ocean, 



coupled with the fact that the inter- 

 national market is now more open to 

 pelagic sharks and their derivatives 

 (Mejuto and de la Serna, 2000). 



Most pelagic sharks are migratory 

 species. Thus, effective management 

 proposals require reliable data that 

 reflect migratory patterns, and mul- 

 tilateral international agreements are 

 needed between all Mediterranean 

 countries involved. During the last 

 40-year period, Spanish, Italian, and 

 Greek longline and driftnet fleets 

 have operated throughout the Medi- 

 terranean, targeting mainly sword- 

 fish or albacore and bluefin tuna. 

 Catches began to expand slowly af- 

 ter 1962, increased rapidly with the 

 advent of monofilament driftnets, and 

 peaked in the late 1980s (Anonymous, 

 1999). Until recent years sharks were 

 the most abundant incidental catch 

 (landed, but not specifically targeted, 

 or discarded). But they may become 



