Abstract
The high level of escapes from Atlantic salmon farms, up to two million fishes per year in the North Atlantic, has raised concern about the potential impact on wild populations. We report on a two-generation experiment examining the estimated lifetime successes, relative to wild natives, of farm, F(1) and F(2) hybrids and BC(1) backcrosses to wild and farm salmon. Offspring of farm and "hybrids" (i.e. all F(1), F(2) and BC(1) groups) showed reduced survival compared with wild salmon but grew faster as juveniles and displaced wild parr, which as a group were significantly smaller. Where suitable habitat for these emigrant parr is absent, this competition would result in reduced wild smolt production. In the experimental conditions, where emigrants survived downstream, the relative estimated lifetime success ranged from 2% (farm) to 89% (BC(1) wild) of that of wild salmon, indicating additive genetic variation for survival. Wild salmon primarily returned to fresh water after one sea winter (1SW) but farm and 'hybrids' produced proportionately more 2SW salmon. However, lower overall survival means that this would result in reduced recruitment despite increased 2SW fecundity. We thus demonstrate that interaction of farm with wild salmon results in lowered fitness, with repeated escapes causing cumulative fitness depression and potentially an extinction vortex in vulnerable populations.
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Selected References
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- Cairney M., Taggart J. B., Høyheim B. Characterization of microsatellite and minisatellite loci in Atlantic salmon (Salmo salar L.) and cross-species amplification in other salmonids. Mol Ecol. 2000 Dec;9(12):2175–2178. [PubMed] [Google Scholar]
- Fleming I. A., Hindar K., Mjølnerød I. B., Jonsson B., Balstad T., Lamberg A. Lifetime success and interactions of farm salmon invading a native population. Proc Biol Sci. 2000 Aug 7;267(1452):1517–1523. doi: 10.1098/rspb.2000.1173. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jönsson E., Johnsson J. I., Björnsson B. T. Growth hormone increases predation exposure of rainbow trout. Proc Biol Sci. 1996 May 22;263(1370):647–651. doi: 10.1098/rspb.1996.0097. [DOI] [PubMed] [Google Scholar]
- Martinez J. L., Moran P., Perez J., De Gaudemar B., Beall E., Garcia-Vazquez E. Multiple paternity increases effective size of southern Atlantic salmon populations. Mol Ecol. 2000 Mar;9(3):293–298. doi: 10.1046/j.1365-294x.2000.00857.x. [DOI] [PubMed] [Google Scholar]
- McDowell Natasha. Africa hungry for conventional food as biotech row drags on. Nature. 2002 Aug 8;418(6898):571–572. doi: 10.1038/418571a. [DOI] [PubMed] [Google Scholar]
- doi: 10.1098/rspb.1997.0031. [DOI] [PMC free article] [Google Scholar]
- Taggart J. B., McLaren I. S., Hay D. W., Webb J. H., Youngson A. F. Spawning success in Atlantic salmon (Salmo salar L.): a long-term DNA profiling-based study conducted in a natural stream. Mol Ecol. 2001 Apr;10(4):1047–1060. doi: 10.1046/j.1365-294x.2001.01254.x. [DOI] [PubMed] [Google Scholar]
- Tufto Jarle, Hindar Kjetil. Effective size in management and conservation of subdivided populations. J Theor Biol. 2003 Jun 7;222(3):273–281. doi: 10.1016/s0022-5193(03)00018-3. [DOI] [PubMed] [Google Scholar]
- Wilkins N. P., Cotter D., O'Maoiléidigh N. Ocean migration and recaptures of tagged, triploid, mixed-sex and all-female Atlantic salmon (Salmo salar L.) released from rivers in Ireland. Genetica. 2001;111(1-3):197–212. doi: 10.1023/a:1013784524894. [DOI] [PubMed] [Google Scholar]