suggested that the Alboran Sea and nearby areas could be a postpartum bycatch area
for the common thresher. This suggestion is in line with observations of kayak sport
fishing bycatch, where juvenile individuals are taken as bycatch next to the coast
(Báez et al. 2016). Regarding bigeye thresher (Alopias superciliosus), scientific
studies have suggested the existence of a nursery area in waters off the southwestern
Iberian peninsula (Moreno and Moron 1992).
The Lamnidae family (Lamnidae) includes important charismatic species such as
the white shark (Carcharodon carcharias). This species uses the Alboran Sea as an
occasional route rather than as a residential area as it follows sea turtles and
cetaceans from Atlantic waters (Morey et al. 2003). The shortfin mako is the best
representative of this family. Although the fishing fleet was less industrialized in the
past than nowadays, these sharks were eagerly sought by fishermen because the
dried meat of shortfin mako was considered a delicacy and was often served as
swordfish (Báez 2001). Since ancient times, surface longliners have been called
“marrajeras” (and their crew “marrajeros”), a name derived from the word
“marrajo”, which was the common Spanish name of shortfin mako. Because of the
decrease in its numbers, current captures are always sporadic, and therefore the sale
of this species is not profitable. In fact, when longliners were targeting shortfin mako
for commercial purposes, wire leaders instead of nylon leaders were used on the
snoods—as currently used in the Mediterranean—which were more resistant to
shark bites (Báez 2001).
The basking shark (Cetorhinus maximus, Cetorhinidae) crosses the Alboran Sea,
including near the coast, during January, March, and May (Valeiras et al. 2001).
Using data collected in the south of Portugal, Couto et al. (2017) showed that the
occurrence of basking sharks in this area was related to the beginning of the
upwelling season and that the inter-annual changes were related to lower sea surface
temperatures. These results suggest that basking sharks are associated with the
expansion of cold waters following upwelling events in the region, which is probably due to the aggregation and increase of zooplankton (Couto et al. 2017). Greater
concentrations of basking sharks in the south of Portugal are associated with
increased numbers passing through the Alboran Sea.
The Carcharhinidae family includes the blue shark, which is the most abundant
pelagic shark in the Alboran Sea. For a few weeks of the year, several longliners
based in Alboran ports target blue shark. Although their sale price is low, this is
compensated for by their great abundance and proximity to landing ports. MuñozChápuli (1984) observed that juvenile blue sharks remain in nursery and feeding
areas and do not migrate until they reach an average length of 130 cm. The average
size of blue sharks caught in the Gulf of Cádiz and the Mediterranean is 111 and
153 cm, respectively. These individuals are clearly immature, given that adult
specimens are fertile after reaching a length of 217 cm (Macías et al. 2015). Thus,
the Mediterranean and adjacent waters could be functioning as a juvenile nursery
and feeding area. Macías et al. (2015) found that females predominate in the Alboran
Sea, whereas males predominate in the central North Atlantic: however, the sex ratio
is close to 50% in the Mediterranean. These observations suggest that juvenile blue
sharks are segregated by sex and age in the Mediterranean Sea and adjacent waters.
21 Marine Megafauna and Charismatic Vertebrate Species
709
for the common thresher. This suggestion is in line with observations of kayak sport
fishing bycatch, where juvenile individuals are taken as bycatch next to the coast
(Báez et al. 2016). Regarding bigeye thresher (Alopias superciliosus), scientific
studies have suggested the existence of a nursery area in waters off the southwestern
Iberian peninsula (Moreno and Moron 1992).
The Lamnidae family (Lamnidae) includes important charismatic species such as
the white shark (Carcharodon carcharias). This species uses the Alboran Sea as an
occasional route rather than as a residential area as it follows sea turtles and
cetaceans from Atlantic waters (Morey et al. 2003). The shortfin mako is the best
representative of this family. Although the fishing fleet was less industrialized in the
past than nowadays, these sharks were eagerly sought by fishermen because the
dried meat of shortfin mako was considered a delicacy and was often served as
swordfish (Báez 2001). Since ancient times, surface longliners have been called
“marrajeras” (and their crew “marrajeros”), a name derived from the word
“marrajo”, which was the common Spanish name of shortfin mako. Because of the
decrease in its numbers, current captures are always sporadic, and therefore the sale
of this species is not profitable. In fact, when longliners were targeting shortfin mako
for commercial purposes, wire leaders instead of nylon leaders were used on the
snoods—as currently used in the Mediterranean—which were more resistant to
shark bites (Báez 2001).
The basking shark (Cetorhinus maximus, Cetorhinidae) crosses the Alboran Sea,
including near the coast, during January, March, and May (Valeiras et al. 2001).
Using data collected in the south of Portugal, Couto et al. (2017) showed that the
occurrence of basking sharks in this area was related to the beginning of the
upwelling season and that the inter-annual changes were related to lower sea surface
temperatures. These results suggest that basking sharks are associated with the
expansion of cold waters following upwelling events in the region, which is probably due to the aggregation and increase of zooplankton (Couto et al. 2017). Greater
concentrations of basking sharks in the south of Portugal are associated with
increased numbers passing through the Alboran Sea.
The Carcharhinidae family includes the blue shark, which is the most abundant
pelagic shark in the Alboran Sea. For a few weeks of the year, several longliners
based in Alboran ports target blue shark. Although their sale price is low, this is
compensated for by their great abundance and proximity to landing ports. MuñozChápuli (1984) observed that juvenile blue sharks remain in nursery and feeding
areas and do not migrate until they reach an average length of 130 cm. The average
size of blue sharks caught in the Gulf of Cádiz and the Mediterranean is 111 and
153 cm, respectively. These individuals are clearly immature, given that adult
specimens are fertile after reaching a length of 217 cm (Macías et al. 2015). Thus,
the Mediterranean and adjacent waters could be functioning as a juvenile nursery
and feeding area. Macías et al. (2015) found that females predominate in the Alboran
Sea, whereas males predominate in the central North Atlantic: however, the sex ratio
is close to 50% in the Mediterranean. These observations suggest that juvenile blue
sharks are segregated by sex and age in the Mediterranean Sea and adjacent waters.
21 Marine Megafauna and Charismatic Vertebrate Species
709