| | Population genetics of finfish |
| 301 | Basic genetic principles should be applied to all culture programmes, whether for conservation, stocking or human consumption, although each goal will require a separate breeding methodology. |
| 302 | The development of mitochondrial DNA studies by restriction enzymesshould be encouraged to obtain a finer definition of population structure, efficient markers of gene flow and phylogenetic information. |
| 303 | Further screening of allozymic variation that may be correlated with quantitative traits should be carried out. |
| 304 | Multiple-approach methodologies should be adopted to simplify the “translation” of results obtained into practical applications. |
| 305 | Parental stocks should be sampled from the entire period of spawning (where applicable) to avoid changing the biological parameters of the population and decreasing population variability and yield in the long run. |
| 306 | It should be considered that overfishing of natural stocks, besides causing a reduction in size and age, also alters the genetic structure of the stocks. |
| | Population genetics of crustaceans and molluscs |
| 307 | The above recommendations 301–304 also apply fully or partially. |
| 308 | Studies on techniques to improve control over crustacean reproductionshould be encouraged. |
| 309 | In molluscs, the amount of intrapopulational variation is so great that the use of advanced mathematical methods is needed to obtain more detailed knowledge on the genetic structure of the variability. |
| 310 | There is some doubt that one can simultaneously select for both larval survival and growth in molluscs. |
| | General recommendations for population genetics |
| 311 | Historically well-established natural gene pools should be protected as they are the prerequisite to any successful breeding programme. |
| 312 | Aquaculture manuals for broodstock management and breeding practices should be prepared, based on accepted genetic principles. |
| 313 | The causes and extent of temporal variability in gene frequencies should be studied. |
| 314 | Further development of multi-dimensional techniques should be encouraged to obtain a better understanding of the genetic composition of wild and hatchery populations. |
| 321 | In designing a selection programme for disease tolerance, a decision must be made between selection for response to a specific disease or for a non-specific immune response. Consideration must also be given as to whether a resistant fish can be a carrier of pathogens. Results from selection programmes for specific diseases may develop too slowly compared to the rate of mutation and of adaptation of pathogens. In some cases, vaccination or chemotherapy may be more efficient. Selected immune response and vaccination may be additive factors. |
| 322 | Age at maturation is a complex trait. Examination of growth patterns of individual salmonids show that high growth rates in the winter previous to maturation promote maturation percentages. Maturation in itself may trigger accelerated growth in the early maturation phase. Total growth rates of maturing fish in the maturation year were lower than for non-maturing fish. It is perhaps most feasible to combine genetic and environmental factors for this trait: to select fish for high growth rates and simultaneously to use environmental manipulation to depress maturation. |
| 323 | All additive genetic variances should be expressed in terms of paternal components, in view of the wide variations in egg quality due to non-genetic factors. |
| 324 | Further documentation on the absolute and relative effectiveness of the different selection strategies, particularly under commercial conditions should be urgently provided. |
| 325 | Genotype-X-environment-interaction studies should be encouraged in different countries and standardized procedures should be developed for such studies. |
