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T. Dempster and P. Sanchez-Jerez
species of wild fish aggregate at farms, although only 1 to 3 taxa (principally
Mugilidae, Trachurus mediterraneus, Sardinella aurita and Boops boops) dominate
the assemblages (Dempster et al. 2002; Boyra et al. 2004; Tuya et al. 2005;
Dempster et al. 2005). The sizes of aggregated planktivorous fish at farms in
Mediterranean Spain are large and most are likely to be adult (85% adult: Dempster
et al. 2002; 71% adult: Dempster et al. 2005). In cold-water areas, such as Scotland
and Norway, fewer species have been noted to associate with farms (Pollachius
virens; Carss 1990; Bjordal and Skar 1992), however, no extensive surveys of the
wild fish that are attracted to high-latitude farms have been undertaken to date.
Indirect evidence suggests that these fish are also predominantly adult, as a large
proportion of wild saithe tagged after capture from beneath a Norwegian salmon
farm migrated to offshore spawning grounds (Bjordal and Skar 1992).
Aggregations of demersal fish also occur beneath farms although aggregation
size varies greatly between locations; few demersal fish occur beneath farms in
Mediterranean Spain while large, multi-species aggregations occur under farms
in the Canary Islands (Dempster et al. 2005). Large abundances of sparids such as
Pagellus sp., large Chondrichthyid rays (8 species) and Heteroconger longissimus
have been observed at farms in the Canary Islands (Boyra et al. 2004; Tuya et al.
2005; Dempster et al. 2005). Large, carnivorous fish, such as Pomatomus saltator,
Coryphaena hippurus, and Sphyraena spp. aggregate around many farms
(Dempster et al. 2002; Dempster et al. 2005). P. saltator commonly occurs in
shoals of hundreds to thousands of individuals at farms along the south-east coast
of Spain (Dempster et al. 2002) and feeds mainly on wild Sardinella aurita around
the cages (Sanchez-Jerez et al. unpublished data).
Considerable spatial variability in wild fish abundance and biomass exists among
farms located along the same stretch of coastline (Dempster et al. 2002). Aggregations
Fig. 3.4 Aggregations of wild fish near the bottom (left) and the surface (right) of a coastal seacage sea bream farm in the Canary Islands, Atlantic Ocean. (Photo courtesy of Arturo Boyra,
www.oceanografica.com)
T. Dempster and P. Sanchez-Jerez
species of wild fish aggregate at farms, although only 1 to 3 taxa (principally
Mugilidae, Trachurus mediterraneus, Sardinella aurita and Boops boops) dominate
the assemblages (Dempster et al. 2002; Boyra et al. 2004; Tuya et al. 2005;
Dempster et al. 2005). The sizes of aggregated planktivorous fish at farms in
Mediterranean Spain are large and most are likely to be adult (85% adult: Dempster
et al. 2002; 71% adult: Dempster et al. 2005). In cold-water areas, such as Scotland
and Norway, fewer species have been noted to associate with farms (Pollachius
virens; Carss 1990; Bjordal and Skar 1992), however, no extensive surveys of the
wild fish that are attracted to high-latitude farms have been undertaken to date.
Indirect evidence suggests that these fish are also predominantly adult, as a large
proportion of wild saithe tagged after capture from beneath a Norwegian salmon
farm migrated to offshore spawning grounds (Bjordal and Skar 1992).
Aggregations of demersal fish also occur beneath farms although aggregation
size varies greatly between locations; few demersal fish occur beneath farms in
Mediterranean Spain while large, multi-species aggregations occur under farms
in the Canary Islands (Dempster et al. 2005). Large abundances of sparids such as
Pagellus sp., large Chondrichthyid rays (8 species) and Heteroconger longissimus
have been observed at farms in the Canary Islands (Boyra et al. 2004; Tuya et al.
2005; Dempster et al. 2005). Large, carnivorous fish, such as Pomatomus saltator,
Coryphaena hippurus, and Sphyraena spp. aggregate around many farms
(Dempster et al. 2002; Dempster et al. 2005). P. saltator commonly occurs in
shoals of hundreds to thousands of individuals at farms along the south-east coast
of Spain (Dempster et al. 2002) and feeds mainly on wild Sardinella aurita around
the cages (Sanchez-Jerez et al. unpublished data).
Considerable spatial variability in wild fish abundance and biomass exists among
farms located along the same stretch of coastline (Dempster et al. 2002). Aggregations
Fig. 3.4 Aggregations of wild fish near the bottom (left) and the surface (right) of a coastal seacage sea bream farm in the Canary Islands, Atlantic Ocean. (Photo courtesy of Arturo Boyra,
www.oceanografica.com)