Genetic population structure in flatfishes and potential impact of aquaculture and stock enhancement on wild populations in Europe

Abstract

Marine fish wild stocks are known to be heavily depleted by overfishing and flatfish species are no exception. Wild catches being soon insufficient for responding to consumer demand, the cultivation of marine species appeared as a logical response to the need of seafood. Nevertheless, fish aquaculture also entails major impacts on wild populations from which genetic ones are now better known. The hybridization between domestic and native strains potentially have a genetic impact on recipient populations as long as 1) domestic populations are distinct from native wild ones (through domestication process, genetic improvement of captive stocks) and/or 2) the native wild populations are structured (metapopulation structure, local adaptation). Some of the flatfish species exhibit population differentiation and even local adaptation and the release of domestic genetically modified fishes (selected, transgenic) could threaten their survival in case of introgression. The impact of aquaculture on flatfishes is probably still low as land-based farms and low production levels guaranty low rates of escapes and therefore limited contacts between wild and farmed strains. However, flatfish aquaculture is regarded by experts as a rapidly growing domain that will greatly develop soon. In our opinion, this perspective, added to the quite good performances of farmed flatfishes when released into the wild, fully justifies a stronger interest from the scientific community to the conservation of their wild stocks.

Ocean's eleven: a critical evaluation of the role of population, evolutionary and molecular genetics in the management of wild fisheries

“…Stock enhancement is commonly practised to meet the demands of commercial and recreational fishers (Laikre et al 2010). It is most common in freshwater systems that are closed to migration, but is increasingly being used for marine species in estuarine and inshore habitats (Carson et al 2009;Danancher and Garcia-Vazquez 2011). Some releases occur into vacant habitats, such as newly created water impoundments, or into habitats without a conspecific [see Glossary (Data S1)] resident population.…”

Parallel evolution and adaptation to environmental factors in a marine flatfish: Implications for fisheries and aquaculture management of the turbot (Scophthalmus maximus)

“…The detection of genetic structure in marine species represents a challenge due to generally high effective population sizes and high gene flow facilitated by the absence of physical barriers, which lead to genomic homogenization across populations (Danancher & Garcia‐Vazquez, 2011; Vandamme et al., 2014; Vilas et al., 2015). However, various factors can bring about genetic differentiation, such as habitat shifts (ecotones) and oceanic currents (Blanco‐Gonzalez, Knutsen, & Jorde, 2016; Galarza et al., 2009; Nielsen, Nielsen, Meldrup, & Hansen, 2004; Vera et al., 2016a), and natural selection in response to environmental variation (Milano et al., 2014; Vandamme et al., 2014; Vilas, Bouza, Vera, Millán, & Martínez, 2010; Vilas et al., 2015).…”

Evolutionary Biology: Biodiversification from Genotype to Phenotype

“…They found a drastic reduction of the genetic variability on only one generation in three of the four analyzed stocks due to the incorporation of family-related G1 (first-generation progeny) individuals in their breeder groups, without taking into account for their selection any genetic criteria. Similar losses of genetic variability have also been found in farmed Atlantic halibut Hippoglossus hippoglossus (level 4) and turbot Psetta maxima (level 5) when comparing the F1 generation to their founder wild populations (Damancher and Garcia-Vasquez 2011). The case of European sea bass Dicentrarchus labrax is further described below because it is arguably the fish species for which most of the domestication history and genetic variability are both relatively well known (Vandeputte 2012;Hillen et al 2014).…”