146
T.F. Cross et.al.
for wild populations in areas where interactions occur. In this context the sea louse
Caligus elongatus may become a major threat because it can infect both wild and
farmed salmon and cod. A recently completed EU project (GENIMPACT (www.
genimpact.imr.no)) is considering the genetic aspects of cultured/wild interactions
in European cultured aquatic species.
It is concluded that the likely severity of detrimental effects on individual native
species depends on size and status of native populations, and extent and frequency
of introductions (and on genetic composition of cultured strains). Effects are most
severe where wild populations sizes were historically small and have been further
reduced by overfishing and increased natural mortality (e.g., salmon throughout
their range), and also where introductions are large and regular (annual) and where
cultured strains have undergone several generations of hatchery rearing and strong
artificial selection.
4.9 Recommendations
1. Governmental regulations in different countries should be reviewed to determine
whether these give adequate protection to wild populations potentially threatened
by direct and/or indirect interactions with reared fish or invertebrates.
2. For many species currently reared in Europe and elsewhere there is inadequate
knowledge of the genetic population structure. Detailed investigations are
urgently needed and also some earlier studies will need repeating as more
discriminatory molecular markers become available
3. It should be recognised that entirely different genetic principles are involved in
producing strains for farming under conditions of confinement throughout the
lifecycle, compared with strains for stocking/ranching (or indeed for farming in
the wild without confinement, e.g., for bivalve molluscs).
4. It is recognised that traditional genetic methods of strain improvement by
selection will continue, assisted by Marker Assisted Selection and other novel
molecular techniques. In contrast minimum genetic manipulation should be
applied to organisms to be used for stocking/ ranching.
5. Experiments are urgently required to learn more about domestication selection.
6. Cage/ tank outflow design should be matched to particular site conditions so as
to minimise escapes and potential for interactions.
7. While beyond the defined scope of the current review, it is recognised that there
is a vast and expanding production of marine algae, chiefly in Asia. Because
there is no containment involved in the culture methods, the potential for
introgression with wild populations must be considerable. It is recommended
that the effects of such interaction events be investigated.
8. The production of sterile strains should be considered (note that the production
of single-sex animals of several species is also desired by the aquaculture
industry). While this will ameliorate the genetic effects of direct interaction, it
will do almost nothing to avoid indirect effects.
T.F. Cross et.al.
for wild populations in areas where interactions occur. In this context the sea louse
Caligus elongatus may become a major threat because it can infect both wild and
farmed salmon and cod. A recently completed EU project (GENIMPACT (www.
genimpact.imr.no)) is considering the genetic aspects of cultured/wild interactions
in European cultured aquatic species.
It is concluded that the likely severity of detrimental effects on individual native
species depends on size and status of native populations, and extent and frequency
of introductions (and on genetic composition of cultured strains). Effects are most
severe where wild populations sizes were historically small and have been further
reduced by overfishing and increased natural mortality (e.g., salmon throughout
their range), and also where introductions are large and regular (annual) and where
cultured strains have undergone several generations of hatchery rearing and strong
artificial selection.
4.9 Recommendations
1. Governmental regulations in different countries should be reviewed to determine
whether these give adequate protection to wild populations potentially threatened
by direct and/or indirect interactions with reared fish or invertebrates.
2. For many species currently reared in Europe and elsewhere there is inadequate
knowledge of the genetic population structure. Detailed investigations are
urgently needed and also some earlier studies will need repeating as more
discriminatory molecular markers become available
3. It should be recognised that entirely different genetic principles are involved in
producing strains for farming under conditions of confinement throughout the
lifecycle, compared with strains for stocking/ranching (or indeed for farming in
the wild without confinement, e.g., for bivalve molluscs).
4. It is recognised that traditional genetic methods of strain improvement by
selection will continue, assisted by Marker Assisted Selection and other novel
molecular techniques. In contrast minimum genetic manipulation should be
applied to organisms to be used for stocking/ ranching.
5. Experiments are urgently required to learn more about domestication selection.
6. Cage/ tank outflow design should be matched to particular site conditions so as
to minimise escapes and potential for interactions.
7. While beyond the defined scope of the current review, it is recognised that there
is a vast and expanding production of marine algae, chiefly in Asia. Because
there is no containment involved in the culture methods, the potential for
introgression with wild populations must be considerable. It is recommended
that the effects of such interaction events be investigated.
8. The production of sterile strains should be considered (note that the production
of single-sex animals of several species is also desired by the aquaculture
industry). While this will ameliorate the genetic effects of direct interaction, it
will do almost nothing to avoid indirect effects.