HOW AQUACULTURE POTENTIAL CHANGES DURING DOMESTICATION: SEEKING THE BEST WAY TO MAXIMIZE IT

Emmanouil Diakos*, Pascal Fontaine, Thomas Lecocq

University of Lorraine, INRAE, UR AFPA, Nancy, France

Email: Emmanouil.diakos@univ-lorraine.fr

Introduction

Aquaculture’s contribution to the total fisheries and aquaculture production is growing, projected to be 53% by 2030 (FAO, 2022). However, to ensure food security and sustainability, it is required to increase the diversity of species that dominate global aquaculture (FAO, 2022). Thus, new domestication programs will be required. Domestication is the process by which a species bred in a captive environment, and modified across successive generations from its wild ancestors, becomes more useful to humans who control increasingly its reproduction and food supply. This process has been described through the five ‘levels of domestication’, from the acclimatization of a wild species in a captive environment (level 1) to the partial completion of the life cycle in captivity (level 2), with (level 3) or without gene flow from the wild (level 4), up to the selection for traits of socio-economic importance (level 5) (Teletchea and Fontaine, 2012). Historically, domestication has led to many success stories, with however numerous unfruitful attempts due to increased complexity in terms of time and species specificities that hindered the process (Teletchea, 2019). Success requires certain prerequisites with regards to the species biology and phenotypic plasticity making it able to adapt to the farmed environment (Braithwaite and Salvanes, 2010; Driscoll et al., 2009; Mignon-Grasteau et al., 2005). In captivity growth and survival, behavior, reproduction and nutrition shape among others, the so called ‘aquaculture potential’ being the quantified amount of expression of all traits/biological-functions favorable for domestication and subsequent production (Toomey et al., 2021). However, the aquaculture potential could be modified during the domestication process, according to the management of base populations. Different scenarios of stock management such as no selection, single function (i.e., usually growth-related traits on) selective breeding program (SBP), or multi-function (i.e., selecting on several traits simultaneously) SBP exist. Thus, the right decision for stock management could improve the aquaculture potential and eventually the resilience of stock performance.

Objective of the study

In 2022, we started a domestication program using zebrafish (Danio rerio) collected from the wild (Bangladesh) to monitor the evolution of the aquaculture potential over successive generations. The zebrafish has been chosen due to its short generation intervals, the extended information available on its breeding and biology, and since it has been proposed as a good model for aquaculture research (Piferrer and Ribas, 2020). The goal is to apply and monitor 3 stock management approaches: 1) no selection = random SBP, a 2) single-function SBP, and a 3) multi-function SBP from the onset of domestication, and assess their consequences on the aquaculture potential. Our hypothesis is that the multi-function SBP could maintain a more genetically diverse population to be exploited in selective breeding, compared with the traditionally applied in aquaculture single-function SBP, that may promote deleterious alleles, loss of genetic diversity due to increased selection pressures, and genetic correlations with undesirable traits. It is a major challenge to maintain animals' ability to adapt to an increasingly unstable environment (climate, economic context, societal demands), and we question whether a multi-functional SBP approach could provide that higher level of adaptability even with a compromised growth potential. Thus, to validate our hypothesis a comparison from the onset of domestication is needed, with a single-function SBP, and a random selection SBP as a point of reference.

Methods

We reared separately 11 families from the base (F0) population, under 3 SBPs (Multi-function, Single-function, Random) from the onset of domestication. For each family were assigned 3 tanks, each corresponding to an SBP, in a recirculated Tecniplast™ rack (5 fish per L).  A main prerequisite was to prevent inbreeding, and thus a pedigree was constructed up to the 4th generation that would not allow the breeding of candidates with same ancestry. At tagging size (70 dpf) breeding candidates were tagged with a visible implant elastomer (VIE, Northwest Marine Technology, USA) to allow the recording of a set of easily measured, least invasive, phenotypic traits. Phenotypic traits were categorized in 1) ‘Active traits’ used for the ranking and selection of the best breeding candidates (male and female) from each SBP (Multi- & Single- function, not Random) within family, and 2) ‘Consequence traits’, a broader set of traits (including all Active traits) involving behavioral experiments, a thermal challenge, and disease resistance challenge test, used to monitor the evolution of the aquaculture potential. For the Multi-function SBP active traits were related to growth, reproduction, and welfare, while for the Single-function active traits were only growth-related. Once the best breeding candidates were selected, inter familial mating was performed and a new generation was produced.

Expected Results

This study, currently in progress, require the phenotyping information from more than one generation in captivity in order to be able to assess how the different selective breeding programs shape the evolution of the aquaculture potential. Here is presented the workflow to describe the hypothesis and propose an alternative way that could be beneficial for future domestication efforts in aquaculture, considering animal welfare and sustainable production. However, apparent behavioural differences have been already observed in the mirror test experiment between F0 and F1 (publication in progress), as it has been described that behavioural phenotypes are the first to be altered under domestication and more specifically in one generation in zebrafish (Pasquet, 2018).

References

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