Aquaculture Africa 2023

November 13 - 16, 2023

Lusaka, Zambia

POTENTIAL FOR INCREASED PRODUCTION OF FARMED RAINBOW TROUT Onchorynchus mykiss (WALBAUM, 1792) IN AFRICA THROUGH GENETIC IMPROVEMENT

James E. Barasa* and Sharon I. Lubembe 

 Department of Fisheries and Aquatic Sciences, University of Eldoret, Kenya

jbarasa@uoeld.ac.ke

 



 As a salmonid, the genome of the Rainbow trout Onchorynchus mykiss (Walbaum , 1792) is complex,  with tetraploidy following whole genome duplicatio n (Ss4R) 88 to 103 million years ago. This gives the species enormous evolutionary potential, and possibly drives the ability of the species to survive in many areas outside its native range, under higher temperatures.  With total annual production of 848,051 tonnes in 2018, g lobal lead producers of farmed O . mykiss are Iran, Turkey, Norway, Peru, Denmark, China, Chile, Italy, France, USA, Colombia, Sweden and the UK , with some countries producing up to 190,000 tonnes annually. Only seven countries in Africa farm O. mykiss , with Lesotho producing 2599 tonnes, South Africa (1583), Kenya (598), Morocco (250) , Zimbabwe (90), Malawi (84) and Ethiopia (11) tonnes. This low production in Africa is due to the use of un-improved strains whose production is whittled down by environmental shocks, especially global warming and diseases. Norway and Chile are examples of countries that embraced the use of genetically improved strains of O. mykiss, with increased annual production.  As a model species in scientific and evolutionary research, genomic resources have been developed over the last decades to support genetic improvement of trout. Just like for the Atlantic salmon, a n integrated map of the trout genome now  exists, enabling fine mapping of quantitative trait lo ci (QTL), and the selection of positional candidate genes to support selective breeding. Similarly, QTLs have been identified for disease resistance,  parasite resistance, immunity, growth rate, stress tolerance, upper thermal tolerance, embryonic development, spawning time and early maturation. We argue that African countries could substantially increase production, despite environment shocks , by using these genomic resources to increase accuracy of selection for  more resilient  genotypes that increase annual production.