Environmental and economic impacts of genetic improvement in fish farming

Fish farming has to meet the increased demand in fish products but also many environmental concerns. There is, therefore, a need to explore new ways of reducing environmental impacts while increasing production level, such as genetic improvement realised through selective breeding. The aim of fish breeding is to increase profit by producing faster growing fish with lower feed intake. Genetic improvement is also expected to reduce environmental impacts. However, little is known about the economic and environmental impacts of selective breeding programs for fish. From the whole farm point of view, genetic improvement of a trait can affect feeding strategy and management practices according the factor that limits production at farm level. Evaluating the impact of a genetic improvement requires, therefore, (1) to model the whole farm using a bioeconomic model and (2) to evaluate the environmental impact along the chain through a Life Cycle Assessment approach.
Combining a bioeconomic model and a LCA analysis, we calculated environmental and economic value (ENV and EV) of genetic improvement in growth rate (as thermal growth coefficient, TGC) and feed efficiency (as feed conversion ratio, FCR) in two different farming systems: recirculating aquaculture system (RAS) and sea cages (SC). In RAS, the limiting factors are the nitrogen treatment of the bio-filter and the fish density in rearing tanks at harvest. In SC, the limiting factors are the fish production quota and the oxygen availability in water. ENV and EV were calculated as the difference in profit or in environmental impacts per kilogram of fish between the current population mean for both traits (μt) and the next generation of selective breeding (μt + Δt) for either TGC or FCR. For environmental impacts we investigated, climate change, eutrophication, acidification and use of energy.
The results shows that ENV and EV were both dependent on the limiting factors. Improving TGC does not increase profit (EV is null) nor decrease environmental impacts (ENV are null) in RAS when nitrogen treatment capacity is the limiting factor and in SC when production quota is the limiting factor. On the other hand, improving TGC increased profit (EV is positive) and decrease environmental impacts (ENV are negative) in RAS, when density is the limiting factor and in SC when oxygen availability is the limiting factor. Improving FCR always increase profit (EV is positive) and decrease environmental impacts (ENV are negative) in RAS and in SC whatever the limiting factor is.
These results emphasize the importance of calculating environmental and economic values in the right context to develop efficient future breeding programs considering environmental objectives in aquaculture. FCR seems to be the most important trait to increase profitability and decrease environmental impacts in fish farming. This result emphasizes the need for further studies aiming at better characterising the genetic bases of feed efficiency, especially any possible genetic correlation with growth trait, to implement efficient selective breeding program for improving feed efficiency.