667 
Pelagic sharks associated with the 
swordfish, Xiphias gladius, fishery in 
the eastern North Atlantic Ocean and 
the Strait of Gibraltar 
Valentin Buencuerpo 
Santiago Rios 
Julio Moron 
Departamento de Biologi'a Animal I (Zoologl a), Facultad de Biologla 
Universidad Complutense de Madrid 
28040 Madrid, Spain 
E-mail address: vbuencar@eucmax.sim.ucm.es 
Abstract .—We report on 175 land- 
ings from 106 longline and 69 gillnet 
boats operating in the eastern North 
Atlantic Ocean and Mediterranean Sea, 
July 1991 to July 1992. Information on 
the catch and biology of five shark spe- 
cies (Isurus oxyrinchus , Prionace 
glauca , Alopias superciliosus, Alopias 
vulpinus, and Sphyrna zygaena ) is ana- 
lyzed and contrasted with swordfish 
(. Xiphias gladius) landings. A total of 
51,205 fish were sampled, of which 
40,198 were sharks, 9,990 swordfish, 
and the rest other bony fish. Spatial, 
temporal, and gear analyses were per- 
formed to show the importance of shark 
bycatch in longline and gillnet fisher- 
ies operating from the south of Spain. 
We present information on population 
structures of the shark species, along 
with hypotheses about shortfin mako 
movements as suggested by landing 
data. 
Manuscript accepted 18 February 1998, 
Fish. Bull. 96:667-685 (1998). 
The Spanish longline fleet operates 
in the eastern North Atlantic (FAO 
fishing area 27), north-central At- 
lantic (FAO 34), and the Mediter- 
ranean Sea (FAO 37). Sharks are 
the most important bycatch of 
swordfish (Xiphias gladius Lin- 
naeus, 1758) fishing in all of these 
areas (Moreno and Moron, 1992b; 
Mejuto and Garces 1 ; Mejuto 2 ). The 
fleets use surface longlines to catch 
swordfish and some sharks have 
become target species as well. 
Three types of longliners operate 
along the south Spanish coast: 
“coastal longliners” that fish two to 
five days in the area of the Strait of 
Gibraltar and that in some cases 
use gill nets in spring and summer; 
“offshore longliners” that spend 15 
to 25 days fishing as far south as 
Senegal; and “long distance freezer 
longliners” that operate mainly in 
the tropical Atlantic Ocean (Gulf of 
Guinea and off Brazil). Little is 
known about shark fishing off 
southern Spain (Garcia, 1970; 
Bravo and Santaella, 1973; Amorin 
et al., 1979; Garces and Rey, 1983; 
Moreno and Moron, 1992b); more is 
known about shark catches from the 
northern Spanish longline fleet 
(Mejuto and Garces 1 ; Mejuto 2 ). 
The biology of eastern Atlantic 
pelagic sharks has not been well 
investigated although detailed taxo- 
nomic studies (Moreno, 1982), morph- 
ology and growth studies ( Blasco and 
Munoz-Chapuli, 1981; Munoz- 
Chapuli and Blasco, 1984; Moreno 
and Moron, 1992b), reproduction 
(Munoz-Chapuli, 1984; Moreno et ah, 
1989; Moreno and Moron, 1992a), and 
faunistic studies (Belloc, 1934; 
Lozano Cabo, 1950; Bravo, 1974; 
Bravo 3 ) are available. 
The most common shark species 
taken by longliners are blue shark, 
Prionace glauca (Linnaeus, 1758) 
and shortfin mako shark, Isurus 
oxyrinchus Rafmesque, 1810, which 
represent 80% of the total shark 
bycatch (Garces and Rey, 1983; 
Moreno and Moron, 1992b). Other 
sharks caught include the por- 
beagle, Lamna nasus (Bonnaterre, 
1788), the hammerheads, Sphyrna 
spp., the bigeye thresher, Alopias 
superciliosus (Lowe, 1839), the com- 
mon thresher, Alopias vulpinus 
1 Mejuto, J., and A. Garces. 1984. 
Shortfin mako, Isurus oxyrinchus, and por- 
beagle, Lamna nasus , associated with 
longline swordfish fishery in NW and N 
Spain. ICES, Council Meeting 1984/G: 72. 
2 Mejuto, J. 1985 Associated catches of 
sharks, Prionace glauca, Isurus oxyrinchus 
and Lamna nasus, with NW and N Span- 
ish swordfish fishery, in 1984. ICES, Coun- 
cil Meeting 1985/H: 42. 
3 Bravo, J. 1973. Elasmobranchii off Ca- 
nary Islands. ICES, Council Meeting 1973/ 
J: 17. 
