Genetic selection leads to more efficient sea bass

MOTS-CLES : aquaculture ; genetic improvement; efficiency

Aquaculture is one of the fastest growing livestock products in the world and is the only way to meet the increasing demand for aquatic products due to the depletion of fish stocks in the oceans. Feed efficiency, which measures the yield of the transformation of feed in fish, is a key factor to a sustainable development on economic (better profitability), ecologic (decrease of intrants and biological waste) and social (reduction of animal feed competition/human food) levels. Life Cycle Assessment studies show the paramount importance of improving feed efficiency to reduce the overall impacts of fish farming (Besson et al., 2016, 2017).

Genetic selection is a potentially important lever for the improvement of feed efficiency, but it has not been applied to fish for the following reasons 1) the absence of a method to measure individual food intake in fish raised in groups and 2) the absence of indirect selection criteria that can be used in practice.

As part of the H2020 EMBRIC project (2015-2019), we tested in sea bass, a major Mediterranean aquaculture species, a method that combines individual phentoyping for feed efficiency in fish isolated in aquariums and genomic selection to improve feed efficiency in this species.

After phentoyping and genotyping 400 sea bass in individual aquariums at Ifremer of Palavas, we showed that individual feed efficiency had a high variability and high heritability (0.47), proof of an efficient genetic selection. We also showed that individual performance in part predicted the group performance (under normal breeding conditions), which is an important trait. In fact, we found a criteria easier to measure and which was also highly heritable: growth in an aquarium under restricted feeding, which was highly genetically correlated to feed efficiency (0.98). Finally, we showed that genomic selection based on a reference population of 360 individuals provides an accuracy that is already usable in practice for genetic evaluation, although more individuals could still improve it.

Based on these results, we were able to finance a similar experiment on the sea bream as part of the PerformFish H2020 project, in partnership with the main French breeder of this species, La Ferme Marine du Douhet and with the Syndicat des Sélectionneurs Avicoles et Aquacoles Français (Sysaaf), in order to test the genericity of the approach. This study is currently underway.

Sea bass lines selected for individual food efficiency have been developed at Ifremer of Palavas, our key partner in this project. These lines will be evaluated in 2020 as part of the H2020 AquaIMPACT project, in order to validate the transgenerational method.

Finally, Ifremer, the Sysaaf and the Ecloserie Marine de Gravelines (EMG) obtained an Innovation FEAMP project (Selfie, 2019-2022) to test the feasabibility of the method on the sea bass population in EMG selection.

The prospects therefore include both a validation on other species and populations, and the beginning of a transfer to fish selection operators.