ReviewThe importance of selective breeding in aquaculture to meet future demands for animal protein: A review
Highlights
► We demonstrate existence of vast potential for increased aquaculture production. ► The largest potential for aquaculture lies in the marine environment. ► Selection responses in aquaculture species are higher than for conventional livestock. ► More use of genetically improved stocks may dramatically increase aquaculture output. ► Genetically improved stocks are critical for better utilization of limited resources.
Introduction
Humanity's greatest problem has been to secure food suitable to meet nutritional needs. It has been said that, ‘Without food, nothing else matters’ (Warwick and Legates, 1979). Many areas of the world currently lack adequate food supplies. Of the 2009 population of 6.7 billion people, 960 million were undernourished (Johnson, 2009), and the human population is predicted to increase to 9.1 billion by 2050 (Diouf, 2009). This population growth, combined with increased average income and increased urbanization with associated shifts in diet towards more nutritious and higher quality foods, is expected to result in almost a doubling of the demand for food (Diouf, 2009). This illustrates that a serious food crisis already exists, and is expected to increase in coming years. It is an enormous task to increase food production to meet the future demand.
When discussing the food crisis Kutty (2010) points out that our long-term perspectives about providing adequate food for the world's growing population have to change dramatically. The same author further states that, ‘The land-based food production systems, despite further expansion and intensification, are limited. We have to turn to water and not too much to land for additional food production, through available sustainable technologies and evolving new innovations, which would ensure our food and nutritional security’. According to Duarte et al. (2009) neither land-based nor marine-based food production alone will suffice to feed humanity in the future, an intelligent integration of marine- and land-based food production is required to meet this essential goal. Marra (2005) discussed the importance of mariculture in the future and argued that a major change in food production is required by moving the production of animal protein from land to the ocean. However, Waggoner (1994) expresses an optimistic view on future plant production: ‘If average fields in the world sixty or seventy years hence, when we are likely to number ten billion, yield as much food as today's potato fields in Ireland, wheat fields in France, or corn fields in Iowa, large portions of the land currently in crops can revert to Nature’. This view is supported by Gjølberg (2010), who argues that many countries can increase agriculture production considerably. He points out that much of the potentially rich agricultural land is actually underutilised, and argues that the solution is to pass on knowledge about fertiliser use and modern agronomy techniques.
With this in mind it is of interest to discuss the role of aquaculture in meeting the future demand for animal protein. Today 53% of fish and shellfish production takes place in freshwater (FAO, 2009) which constitutes only 1% of the globe's surface, while the very large areas covered by sea- and brackish water are currently only marginally utilised. An important part of increasing the future aquaculture production is to improve the biological productivity of farmed species of fish, shellfish (crustacean and molluscs) and seaweeds. The role of selective breeding will therefore be discussed. Investments in well planned and managed breeding programs are unique, because genetic gains obtained in such programs are eternal and cumulative. They are never ‘used up’, and never ‘wear out’ (Weller, 2006).
Quantitative genetics and selective breeding represent a young field of science, and the technology uptake in the aquaculture sector has been slow compared with plant and farm animal industries. Reasons for this are likely to be many and not easily explained. In this review we demonstrate the potential for large genetic improvement in aquatic species and we make some estimations and predictions about the scope for future increased aquaculture production through greater utilisation of genetically improved stocks.
Section snippets
Status of aquaculture production
Asia dominated the world's production of fish and shellfish in 2008 (producing 88% by volume), followed by the Americas, Europe, Africa and Oceania (4.6%, 4.5%, 1.8% and 0.3% respectively, Table 1). Likewise, nearly all seaweed production also takes place in Asia, with China alone producing 2/3 of the world's production (FAO, 2009).
As shown in Table 2, aquaculture production has nearly doubled, and the value of aquaculture products has more than doubled, over the last ten years.
A high
Fish and shellfish for human consumption: comparison with meat from farm animals
Although their nutritional value may vary, fish and shellfish are in general good sources of nutrients. Fish is easily digestible and contains a well balanced amino acid composition. Fish are regarded as healthy, not only because of the content of the omega-3 fatty acids but also because of their content of micronutrients (Centre of Excellence Seafood and Health (CESSH), 2011; Luten, 2008) and amino acids.
The muscle composition of fish and beef is similar, with the exception of the fat content
Efficiency of fish production
Fish are generally more efficient converters of feed into meat than warm blooded animals, due to higher maintenance and respiratory costs for the latter. On average only 2% of the consumed energy is used for biomass production in homeotherms compared with 17% in poikilotherms (Smith, 1992). In Table 7 the retention of energy and protein for Atlantic salmon is compared with pigs and poultry, which are the most efficient meat producing land-based farm animals. The genetically improved salmon had
Growth in aquaculture production
For several years the catch of fish and shellfish has been stable at around 90 million tonnes per year, and the harvest of seaweeds at approx. one million tonnes (FAO, 2009). FAO (2008) stated that ‘The maximum wild capture fisheries potential from the world's oceans has probably been reached’. For aquaculture the situation is different. Aquaculture production of fish and shellfish has grown by an average of 7.7% per year over the last decade (FAO, 2009). No other food production sector shows a
Current status of breeding programs
Modern breeding programs were initiated for plants around 1900 based on the findings from the pioneering hybridization experiments by Mendel (1866), and the same theoretical principles were for the first time applied to terrestrial farm animals some 15 years later (Hagedoorn, 1950). Well-designed breeding programs have since revolutionised the biological efficiency of plant and livestock production through the development of genetically improved, high yielding seed stocks. Aquaculture generally
Interaction between farmed and wild stocks
As domestication and selective breeding of a species progresses, key characteristics of farmed animals will differ more and more from wild stock. Some animals are likely to escape from farms and could interact with the wild stock. The ability of selectively bred escapees to survive, outcompete wild fish and reproduce will no doubt depend on the wild populations, the local environment and ecology, the timing and extent of release(s) and the extent of genetic divergence of the selected stock from
Increased production
From a production point of view there is much to be gained by producing stock which is genetically improved. Basically all applied breeding programs have improvement of growth rate as a major goal, and most results on selection response for growth cited in this paper were obtained when selection targeted growth rate as the only trait. It is expected that gain for the individual traits in selective breeding programs will be reduced as the number of traits under selection is increased.
In order to
Concluding discussion
Early in 2011 FAO declared that ‘1 billion people live in chronic hunger’, which means that there is an ongoing food crisis in the world. Moreover, the world population is expected to increase rapidly in coming years, and Diouf (2009) points out that strong growth in income and urbanization will occur, with associated shifts in diet structure towards more nutritious and higher quality foods. This implies that the demand for animal protein will increase at a high rate. The prospect of future food
Acknowledgements
We are indebted to Nofima for their financial contribution and to our colleagues for continued and stimulating support. In particular we would like to thank Dr. Bjarne Gjerde, who took the initiative to recommend this review, and Dr. Jørgen Ødegård for their valuable contributions.
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