in the baskets is negligible, about 2% (Cano and Campos 2003a, b). The basket
should be cleaned every 3–4 months.
The growth of queen scallops in baskets is high, reaching 57 mm after 1 year of
culture, with negligible mortality (Cano et al. 2006). The results obtained in bags are
worse: queen scallop increases their size from 23 mm to 40 mm in 12 months, and
the mortality rate is higher. Nevertheless, survival could be increased if scallops are
passed to baskets in July or August (Campos and Cano 2004).
The black scallops grow quickly in both baskets and bags, but bags are used to
ongrow spat smaller than 5 mm. Black scallop reaches commercial size (40 mm) at
5 months of fattening in baskets (40 individuals/basket) and at 8 months of fattening
in bags (100 to 200 variegated scallops/bag). In both cases mortality is low at 12%
for baskets and at 9% for bags (Cano et al. 2006).
The culture of pectinids is undertaken via suspension, because in this way the
entire water column is used. Bottom longlines are used for the cultivation of scallops,
so that both, spat settlement and growth, are improved 1–10 m above the bottom. It
also prevents temporary damage to the installation without affecting the structures at
anchor. In addition, the method allows for a greater density of lines, without
problems of entanglements or for navigation since the mother line is at the bottom,
and on the surface only the buoys that mark the ends of it can be seen. In this way,
the number of surface buoys decreases, the possibility of theft or sabotage is
hindered, and these lines are more secure than the temporary lines (López et al.
2005a, b).
Perspectives for the culture of scallops in Andalusia are promising, since large
quantities of seed of the three species are obtained and, subsequently, growth rate is
very fast, with low mortality rate and high population densities.
The main disadvantage for the development of the culture of pectinids is the
proliferation of biotoxin episodes, being mainly those that are produced by
Gymnodinium catenatum (paralytic shellfish poisoning, PSP) and Pseudo-nitzchia
(amnesic shellfish poisoning, ASP), especially in the case of great Atlantic scallop as
it takes a long period of time to eliminate such toxins. Another problem is the
abundance of biofouling, with a very intense fixation of barnacle (Balanus sp.) on all
surfaces in contact with the sea, such as buoys, ropes, baskets, and even on the king
scallops.
In addition, sometimes a very high mortality rate is observed, which is associated
with the presence of crabs, Liocarcinus depurator, Liocarcinus corrugatus, and
Necora puber, particularly concerning Liocarcinus depurator. Other species of
decapods, fish, and octopus could also be present but in smaller quantities. These
species come into the collectors and culture baskets as larvae, and once they grow,
they cannot leave these structures, and consequently they feed on mollusks.
Clam Culture
Banded carpet shell (Venerupis rhomboides, Pennant 1777) is a species of clam that,
years ago, was abundant in the area. At present, there are only a few natural banks
20 Aquaculture in the Alboran Sea
675
should be cleaned every 3–4 months.
The growth of queen scallops in baskets is high, reaching 57 mm after 1 year of
culture, with negligible mortality (Cano et al. 2006). The results obtained in bags are
worse: queen scallop increases their size from 23 mm to 40 mm in 12 months, and
the mortality rate is higher. Nevertheless, survival could be increased if scallops are
passed to baskets in July or August (Campos and Cano 2004).
The black scallops grow quickly in both baskets and bags, but bags are used to
ongrow spat smaller than 5 mm. Black scallop reaches commercial size (40 mm) at
5 months of fattening in baskets (40 individuals/basket) and at 8 months of fattening
in bags (100 to 200 variegated scallops/bag). In both cases mortality is low at 12%
for baskets and at 9% for bags (Cano et al. 2006).
The culture of pectinids is undertaken via suspension, because in this way the
entire water column is used. Bottom longlines are used for the cultivation of scallops,
so that both, spat settlement and growth, are improved 1–10 m above the bottom. It
also prevents temporary damage to the installation without affecting the structures at
anchor. In addition, the method allows for a greater density of lines, without
problems of entanglements or for navigation since the mother line is at the bottom,
and on the surface only the buoys that mark the ends of it can be seen. In this way,
the number of surface buoys decreases, the possibility of theft or sabotage is
hindered, and these lines are more secure than the temporary lines (López et al.
2005a, b).
Perspectives for the culture of scallops in Andalusia are promising, since large
quantities of seed of the three species are obtained and, subsequently, growth rate is
very fast, with low mortality rate and high population densities.
The main disadvantage for the development of the culture of pectinids is the
proliferation of biotoxin episodes, being mainly those that are produced by
Gymnodinium catenatum (paralytic shellfish poisoning, PSP) and Pseudo-nitzchia
(amnesic shellfish poisoning, ASP), especially in the case of great Atlantic scallop as
it takes a long period of time to eliminate such toxins. Another problem is the
abundance of biofouling, with a very intense fixation of barnacle (Balanus sp.) on all
surfaces in contact with the sea, such as buoys, ropes, baskets, and even on the king
scallops.
In addition, sometimes a very high mortality rate is observed, which is associated
with the presence of crabs, Liocarcinus depurator, Liocarcinus corrugatus, and
Necora puber, particularly concerning Liocarcinus depurator. Other species of
decapods, fish, and octopus could also be present but in smaller quantities. These
species come into the collectors and culture baskets as larvae, and once they grow,
they cannot leave these structures, and consequently they feed on mollusks.
Clam Culture
Banded carpet shell (Venerupis rhomboides, Pennant 1777) is a species of clam that,
years ago, was abundant in the area. At present, there are only a few natural banks
20 Aquaculture in the Alboran Sea
675