10 SEPTEMBER 2012 World aquaculture production has grown 7.1 percent per year during 2000 - 2009 and reached 55.7 million t of fish and shellfish and 17.3 t of aquatic plants in 2009 (FAO 2011). If expansion of fish and shellfish continues, production will reach 68.4 million t in 2012, which is greater than the amount projected from capture fisheries (FAO 2009). The prognosis is that fisheries production will stabilize at around 90 million t in the coming years (FAO 2008). The potential for further growth in aquaculture production seems to be very good, considering coastal and land areas suitable for aquaculture in different countries. However, competing activities in these areas and a lack of availability of feed may limit expansion. Production of shellfish and to some extent herbivorous fish species opens possibilities for harvesting some of the extensive primary production that occurs naturally in the sea because these species feed on algae and other plankton. Combining fish, shellfish and seaweed (IMTA; integrated multi-trophic aquaculture) is an interesting concept for sustainable development (Chopin 2011). Production of diadromous and marine species is low compared to freshwater species (Table 1). This is somewhat surprising because the potential for aquaculture production is much larger in the marine environment compared to freshwater. Differences in value among groups of species should be noted. Highly prized species—diadromous and marine fishes and crustaceans—are usually produced under intensive farming conditions compared to freshwater fishes, where lower-priced cyprinids represented 76 percent in 2005 (FAO 2007). The main purpose of this paper is to discuss the role selective breeding can have on the potential expansion and efficiency of future aquaculture production. Status of Breeding Programs for Aquatic Species The majority of fish culturists raise animals derived from wild stocks or from those that have been selected for only a few generations. In contrast, genetically improved stocks and seeds are widely used in terrestrial farm animal and plant production. Thus, fish culture lags far behind terrestrial animal husbandry and plant production (Tave 1986). In surveys, Neira (2010) and Rye et al. (2010) recorded 101 family-based breeding programs in aquaculture, emphasizing that there may be more. Based on these, 8.2 percent of world aquaculture production is estimated to be based on family breeding programs (Gjedrem et al. 2012). There has been slight improvement since previous estimates: 1 percent in 1993 (Gjedrem 1997) and 5 percent in 2002 (Gjedrem 2004). In addition, some commercial farms may undertake some individual selection for growth rate but the majority of aquaculture production is based on wild individuals or stocks that are not genetically improved. What Has Been Accomplished? Over the last 30 years, a number of selection experiments have been carried out (summarized by Gjedrem and Thodesen 2005). The average genetic gain from 12 estimates of growth rate in different fish species was 15 percent per generation, two estimates for shrimp report 8 percent, four estimates for oysters report 14 percent, one estimate for clams reports 9 percent and two estimates for scallops report 17 percent. The average of 21 estimates was 14 percent genetic gain per generation. Similar levels of genetic gain are reported for coho salmon (Neira et al. 2006), channel catfish (Rezk et al. 2003), and European sea bass (Vandeputte et al. 2009). This indicates that growth rates can be more than doubled in less than six generations of selection. Two examples have shown that this has been accomplished. Example 1: Nile tilapia (Oreochromis niloticus), Philippines The base population consisted of hybrids among eight strains that were used to make the GIFT strain. Selection was for growth rate only. The response during five generations of selection was 85 percent (17 percent per generation) (Bentsen et al. 2003). Fish of the GIFT strain have been distributed to several countries. According to Neira (2010), 10 of 20 tilapia family breeding programs are a continuation of GIFT. One of these breeding programs, mainly based on the fifth GIFT generation, has resulted in a further genetic gain of 59 percent after 6 generations of a multi-trait selection program (Thodesen et al. 2011). Example 2: Atlantic salmon (Salmo salar), Norway Four base populations based on 41 wild strains were established (Gjedrem 2010). The first round of selection started in 1975. Thodesen et al. (1999) studied the response over five generations of selection in one of the populations by comparing selected and wild animals. Selection was mainly for growth rate, with some emphasis on age at sexual maturity. Improvement in growth rate was 113 percent or 22 percent per generation. In addition, the correlated effects of protein and energy retention Development of Breeding Programs for Aquatic Species Should be Given High Priority Trygve Gjedrem 1 and Kari Kolstad It should no longer be acceptable that 90 percent of aquaculture production is based on wild and genetically unimproved animals.
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