Context and aims
One way to promote the aquaculture sector sustaina bility relies on the production diversification, notably through the domestication of new species. However, domesticating new species remains a long and challenging process often resulting in unfruitful attempts because of technical issues, socio-economic limitations, or biological features of species
. Most incipient domestication programs often consider species as a unity, disregarding a part of the biodiversity: the wild intraspecific geographic differentiation. Yet, this differentiation can shape local genetic, phenotypic, and ecologic specificities, affecting the domestication predisposition or the socio-economic attractiveness of a particular population
. Therefore, choosing wild populations exhibiting a high potential for aquaculture (i.e. presenting interesting expression of key traits) could facilitate the domestication and production of new species. Here, we (i ) introduce a new method to integrate geographic differentiation in domestication programs and (ii) apply it on a species of interest for inland aquaculture diversification, the European perch (Perca fluviatilis).
A 3-step integrative approach to integrate geographic differentiation in domestication programs
W e propose a 3-step integrative approach to standardize and facilitate new domestication attempts by taking advantage of wild geographic differentiation
. Step 1 consists of classifying the wild biodiversity to identify prospective units (i.e. groups of genetically differentiated allopatric populations), which are likely divergent for key traits. Step 2 aims at comparing performances of these units in standardized conditions (i.e. rearing system) through a multi-function and multi-trait assessment. Finally, step 3 highlights units with highest potential for aquaculture through the calculation of an aquaculture potential score.
The European perch case study
The 3-step integrative approach has been applied to compare the aquaculture potential among prospective units of the European perch
. More specifically, we aimed at finding units with the best performance in larviculture , a critical stage in the P. fluviatilis production . The step 1 allowed identifying five prospective units across 84 West-Palearctic sampling sites using mitochondrial and microsatellite markers : the European Plain, Danube, Northern and Eastern Fennoscandia, Eastern Europe, and the Balkans units. At the step 2, we compared performances of key traits for fish larviculture for three of these prospective units in standardized recirculated aquaculture system. A geographic differentiation was highlighted for six important traits for perch larviculture: survival rate, swim bladder inflation rate, deformity rate, length at hatching, mean of interindividual distances, and change in activity following a stress event. Along with fish farmer-advice-based weighting of the traits, the calculation of an aquaculture potential score allowed identifying, during the step 3, the populations from the Danube region as the most interesting to potentially overcome curren t bottlenecks in European perch larviculture.
Overall, the early applications of the 3 -step approach support that it could allow facilitating domestication of new species or species at incipient stages of domestication which face major bottlenecks. So far applied to fish culture for human consumption , the approach also aims at being extended to other taxa (e.g. crustaceans, mollusks) and other production goals. Nevertheless, the implementation of the approach is still challenging due to some method limitations, pragmatic concerns, and legal regulation constraints needing future improvements to further facilitate aquaculture development.