Genetics and Selection Eva Troianou

 Before selection programs can be started breeding objectives must be defined exactly In Selective Breeding each trait is weighted according to: genetic variation genetic correlation with other traits economic importance.

Traits for improvement are frequently different from one species to another or from one country to another, but there are some traits of high economic importance, that are in common.

1. The most important production phenotype 2. Measurement of body weight or body length  Selective Breeding: o Fish and Shellfish: higher genetic variance compared to farm land animals  7-10% in farmed land animals  20-35% in fish and shellfish higher selection intensity for aquaculture production improvement.

Results of Selection for Growth Rate in fish and shellfish:

 When production is based on using artificial food the FCR improvement is considered to be a primary aim  In carnivorous species  food costs may be a large part of the total production  May fish use less energy for maintenance than farmed land animals, but in fish species under domestication, which they are in continuous stress the maintenance requirements are raised measure of an animals efficiency in converting feed mass into increases of the desired output

 Flesh quality is becoming more and more important, since it is highly related with human health and nutrition  Consumers choice - Competition to other products.  In fish farming it is possible by several means to influence quality (content of feed and feed quality, handling of fish prior to slaughter)  Higher demand of quality improvement in fat fish than other species

Quality requirements may vary from one country to another or change over time. Flesh quality traits of importance: Fat percentage Distribution of Fat Color of flesh Intermascular bones Texture of flesh Condition factor Dressing %

 Considering costs and difficulties of preventing and curing diseases in fish farming, the most effective method can only be the development of natural resistance in fish.  The possible ways of measuring disease resistance are: Survival rate Challenge test Immunological or physiological parameters

 Results of Selection : In Brook Trout: the survival rate changed from 2% to 69% after selecting the surviving fish in a population with furunculosis for three generations (Embody and Hayford, 1925) In Brown Trout: after one generation of selection, mortality due to furunculosis was 2% and 48% among progeny of selected and non-selected parents, respectively (Cipriano and Heartwell, 1986) In Carp: the mortality rate from dropsy was lowered from 51% to 10% within five generations (Kirpichikov, 1987)

 In early maturation the species divert all their energy to gonad production, affecting: growth rate meat quality frequencies of mortality  Fishes become sexually mature at various ages, depending on species and sex  Age of sex maturation is a heritable trait  Strong selection for late maturity will reduce the genetic improvement in growth rate

 In general, improvement of traits can be achieved through the control of Sexual Dimorphism and Sex Maturation in fish and shellfish 1. Polyploidy 2. Sex manipulation 3. Hybridization

The improvement of tolerance in environmental extremes in fish and shell fish species can enhance the Aquaculture production 1. By expanding the range of production in many regions of the world 2. By increased adaptation of species for productive “domestication” better welfare Main Characters  Stress Tolerance  Salinity Tolerance  Cold Tolerance

Stress Tolerance  Environmental stressors are important factors responsible for limit fish performance under aquaculture conditions  Stress  culture density, handling of fish, transport, water quality, use of anesthetics  Stress tolerance improvement would be an indirect mean to increase tolerance to other factors

 Salinity Tolerance With increasing scarcity of fresh water available for aquaculture, especially in arid regions, development of species that tolerate high salinity would increase fish production Approaches to improve salinity tolerance in Tilapia:  Adding salt to feed  Acclimation  Hybridization  Genomic approaches  Selective breeding

 Cold tolerance  recent experiment evidence suggests that some fishes might carry sufficient variation to adapt to temperature cold tolerance should be under selection great economic importance in Tilapia 1.severe mortalities occur during the winter in temperate climate countries 2.the inability of tilapia to tolerate low temperature is of major economic concern as it reduces their growing season

AKVAFORSK

 GENETIC IMPROVEMENT PROGRAMS FOR AQUACULTURE SPECIES IN DEVELOPING COUNTRIES: PROSPECTS AND CHALLENGES R.W. Ponzoni, N. H. Nguyen and H.L. Khaw  GENETIC VARIATION IN QUANTATIVE TRAITS AND SELECTIVE BREEDING IN FISH AND SHELLFISH Trygve Gjerdem, Department of Animal Genetics and Breeding, University of Norway  REVIEW OF THE STATUS OF AQUACULTURE GENETICS Rex A. Dunham1, Kshitish Majumdar, Eric Hallerman, Devin Bartley, Graham Mair, Gideon Hulata, Zhanjiang Liu, Nuanmanee Pongthana, Janos Bakos, David Penman, Modadugu Gupta, Peter Rothlisberg and Gabriele Hoerstgen-Schwark  FLESH QUALITY IMPROVEMENT IN FISH THROUGH BREEDING Trygve Gjedrem, Institute of Aqcuaculture Research, Norway  SELECTION AGAINST EARLY MATURITY IN LARGE RAINBOW TROUT Oncorhyncus mykiss Antti Kause, Ossi Ritola, Tuija Paananen, Esa Mantysan, Unto Eskelinen  SELECTION PROGRAMMES FOR STRESS TOLERANCE IN FISH Alfonso J.M., Gines R., Montero D., Robain l., Fernadez H., Izquidero M.  IMPROVING SALINITY TOLERANCE IN TILAPIAS: A REVIEW Avner Cnaani, Ariel Velan, Gideon Hulata  Cold tolerance of selective breeding of Oreochromis niloticus and oreochromis aureus Mahmoud A. Rezk and Ebtehag A. Kamel