The efficiency and effectiveness of selective breeding programs can be greatly enhanced through the use of DNA technology. The application of such technology will be used for pedigree information and identification of markers for economic traits leading to marker-assisted selection. Although various international laboratories and CSIRO have developed a bank of molecular markers for Atlantic salmon, the potential of these and other nuclear DNA markers such as AFLPs need evaluating.
Through this project we would be able to formally collaborate on an international mapping project for salmonids. This would give the local industry access to far more markers and genetic information than would be possible if we worked in isolation.
The extent of genetic variation within the Tasmanian population with respect to overseas endemic populations remains unclear. In time it may be considered advantageous to import new genetic material to enhance various characteristics of the local population. However, at present that is unlikely and the genetic status of the population, and of the effectiveness of breeding protocols, needs to be better understood. Significant progress was made with this and the search for sex differences (project 96/347), but funding is required to further the research.
Final report
Archived DNA was successfully extracted from 30-year-old dried scales collected in 1971 and 1972 from wild Atlantic salmon from the River Philip, Canada.
Genetic variation was assessed at 11 nuclear DNA microsatellite loci (three tetra- and eight di-nucleotide repeats) in two samples from the River Philip, Canada (1971/72 and 1991 year-classes), one from Gaden, NSW (1997) and seven from the Tasmanian population (1992, and 1996 to 2001 year-classes).
The 1971/72 sample (archived scales) from Canada proved to be a reliable and realistic baseline (compared to the 1991 sample) against which to assess genetic drift in the Tasmanian population.
A highly significant loss of alleles was observed in all hatchery (Canada, Gaden and Tasmanian) produced samples compared to the wild 1971/72 Canada sample. No difference in heterozygosity was observed.
Estimates of per-generation effective population sizes for the Tasmanian Atlantic salmon population, based on allele frequency variance with the 1971/72 Canada sample, ranged from 102 to 207 individuals, with the average value for the last three (1999 to 2001) year-classes of 185 individuals. These values are up to 80% higher than previous estimates based on allele variance comparison with the 1991 Canada sample. The values are consistent with the population having experienced a minor bottleneck early in the introduction to Australia but with subsequent hatchery controlled generations of high effective breeding numbers.
Despite the observed loss of alleles compared to the wild progenitor population our results vindicate the Tasmanian hatchery protocols that have maintained a sufficiently large breeding population to preserve a genetically healthy population.
Keywords: Atlantic salmon, Salmo salar, pedigree, genetic variation, microsatellites, AFLP, AGD resistance, MHC
