4 Interactions of Wild and Reared Fish and Invertebrates
127
performance seems to occur even with salmon introduced as eggs from a nearby
river (McGinnity et al. 2004). It is presently unclear whether there are similar
local adaptational effects in other species, although this is likely to be the case,
and if there are, non-native translocated or reared strains may have lower
Darwinian fitness in the wild, compared with natural native populations (de Eyto
et al. 2007).
Different broodstock strategies apply to producing animals for farming or for
stocking. For farming, a closed cycle will usually be used and all life-stages will
be in captivity. Such activities may also have associated breeding programmes,
where the major goal will be faster growth, with other aspects such as delayed
sexual maturity, carcass quality and disease resistance also being included as
objectives (Gjedrem 1999). Thus, farm strains will diverge genetically from their
wild progenitors and this deliberate divergence will increase as generations in
the breeding programme progress. Recent microarray results from Roberge et al.
(2006) have demonstrated changes in gene expression over generations caused
by breeding programmes. In examinations of entirely separate Atlantic salmon
breeding programmes in Norway and eastern Canada, it was noted that many of
the same genes were up- or down regulated (genetic expression increased or
decreased) when these fish were compared with wild individuals from either
area. Such studies target the functional aspects of expressed genes, rather than
focussing on neutral loci as in many previous molecular studies.
It should be noted that incorporation of breeding programmes into production of
animals for sea farming is regarded an economic imperative by the industry, so it is
unlikely that any Government-initiated protection measure for wild populations will
suggest abandoning such activities because of potential detrimental effects for wild
animals. As alternatives, better containment of farmed fish or invertebrates will be
required and conservation or farm-free areas instigated to protect particularly
vulnerable wild populations.
Genetically Modified (GM) individuals, where the definition of GM used here
is intra- and/or interspecific transgenics (Devlin et al. 1994), will differ from wild
ancestors from the time the transgene is successfully incorporated. European Union
regulations currently prohibit the release of such organisms into the wild, and high
levels of containment are used when they are being developed. However,
transgenesis can greatly increase the growth potential of aquatic animal species
(Devlin et al. 1994), so there is likely to be aquaculture-industry pressure to use
such individuals in the future. If so, there will be the potential for escapes to the
wild. In western Canada, where the deliberate release of transgenic salmon to the
wild is prohibited, desk studies have been carried out to estimate the environmental
impact of escapes of GM Pacific salmon (Devlin et al. 2004).
4.2.1.3 Breeding for Stocking and Ranching
In the preparation of animals for stocking, a totally different breeding strategy is
utilised. Here, the imperative is to keep the strain as near wild as possible, to avoid
127
performance seems to occur even with salmon introduced as eggs from a nearby
river (McGinnity et al. 2004). It is presently unclear whether there are similar
local adaptational effects in other species, although this is likely to be the case,
and if there are, non-native translocated or reared strains may have lower
Darwinian fitness in the wild, compared with natural native populations (de Eyto
et al. 2007).
Different broodstock strategies apply to producing animals for farming or for
stocking. For farming, a closed cycle will usually be used and all life-stages will
be in captivity. Such activities may also have associated breeding programmes,
where the major goal will be faster growth, with other aspects such as delayed
sexual maturity, carcass quality and disease resistance also being included as
objectives (Gjedrem 1999). Thus, farm strains will diverge genetically from their
wild progenitors and this deliberate divergence will increase as generations in
the breeding programme progress. Recent microarray results from Roberge et al.
(2006) have demonstrated changes in gene expression over generations caused
by breeding programmes. In examinations of entirely separate Atlantic salmon
breeding programmes in Norway and eastern Canada, it was noted that many of
the same genes were up- or down regulated (genetic expression increased or
decreased) when these fish were compared with wild individuals from either
area. Such studies target the functional aspects of expressed genes, rather than
focussing on neutral loci as in many previous molecular studies.
It should be noted that incorporation of breeding programmes into production of
animals for sea farming is regarded an economic imperative by the industry, so it is
unlikely that any Government-initiated protection measure for wild populations will
suggest abandoning such activities because of potential detrimental effects for wild
animals. As alternatives, better containment of farmed fish or invertebrates will be
required and conservation or farm-free areas instigated to protect particularly
vulnerable wild populations.
Genetically Modified (GM) individuals, where the definition of GM used here
is intra- and/or interspecific transgenics (Devlin et al. 1994), will differ from wild
ancestors from the time the transgene is successfully incorporated. European Union
regulations currently prohibit the release of such organisms into the wild, and high
levels of containment are used when they are being developed. However,
transgenesis can greatly increase the growth potential of aquatic animal species
(Devlin et al. 1994), so there is likely to be aquaculture-industry pressure to use
such individuals in the future. If so, there will be the potential for escapes to the
wild. In western Canada, where the deliberate release of transgenic salmon to the
wild is prohibited, desk studies have been carried out to estimate the environmental
impact of escapes of GM Pacific salmon (Devlin et al. 2004).
4.2.1.3 Breeding for Stocking and Ranching
In the preparation of animals for stocking, a totally different breeding strategy is
utilised. Here, the imperative is to keep the strain as near wild as possible, to avoid