Can Genetically Improved Farmed Fish Increase Global Aquaculture Productivity?

28 September 2015, at 1:00am

Increased aquaculture production will be needed in future to improve food security, but what role can genetically improved farmed fish species play in increasing productivity? This study from Ingrid Olesen and colleagues investigates.

The annual production from global aquaculture has increased rapidly from 2.6 million tons or 3.9 per cent of the total supply of fish, shellfish and molluscs in 1970, to 66.7 million tons or 42.2 per cent in 2012.

Capture fisheries have more or less levelled out at about 90 million tons per year since the turn of the century, partly because the exploitation has reached or surpassed the carrying capacity of many major fishery stocks.

Consequently, future increase of (or perhaps even maintaining) the global fish supply depends on the further growth of aquaculture production.

For instance, China, the world’s largest producer, consumer, processor, and exporter of finfish and shellfish, produces mainly from its highly expanding aquaculture sector, accounting for approximately 72 per cent of its reported domestic fish production. China alone contributes more than 60 per cent of global aquaculture production volume and roughly half of global aquaculture value.

Aquaculture is the country’s fastest growing food sector (5 per cent to 6 per cent annual growth in volume from 2000 to 2012), and its output reached 40 million metric tons (including molluscs, excluding algae) in 2012, four times the production volume in 1990.

Vietnam is another Southeast Asian country with a tremendous growth of aquaculture production during the past decade (tripled since 2003), exceeding its capture fisheries, and with a need and potential for further expansion.

Terrestrial farm animal production is almost entirely based on populations or breeds that have been genetically domesticated through millennia and are systematically and selectively bred for improved performance often over centuries.

This approach has improved the productivity and resource efficiency of the livestock populations many fold beyond the capacity of their wild ancestors. The development of modern animal husbandry would be impossible without domesticated and genetically improved animals.

Aquaculture probably dates back as far as about 2000 BC with the development of pond culture in East Asia, the Mediterranean and Central America for example, but aquatic animals have not been through a similar process of genetic domestication and selective breeding as terrestrial farm animal species.

Less than 10 per cent of the global aquaculture production is based on genetically improved material from modern breeding programs allowing for control of inbreeding as well as genetic selection.

As a result, the majority of aquaculture production is still based on wild type animals that are usually poorly adapted to life in captivity. This situation implies poor growth rates and animal welfare, high mortality, inefficient use of resources such as feeds, water and energy, and higher cost per kg of fish produced.

Farming of genetically improved fish has the potential to contribute significantly to increased supply of fish, including in those regions and countries with significant food security and nutrition challenges.

The two major aquaculture species under domestication worldwide are Atlantic salmon and Nile tilapia (3.1 per cent and 4.8 per cent of the global production), which have been subjected to more than 40 years (10 generations) and 20 years (15-20 generations) of selective breeding, respectively.

However, most of the production of other important aquaculture species such as carps and other cyprinids (38 per cent of the global aquaculture production) is based on stocks that are not expected to differ largely from wild type animals.

Still, the feed conversion efficiency of many farmed fish species is higher than that of domesticated terrestrial farm animals, partly because of lower energy requirements for body thermo-regulation.

Furthermore, an increasing number of studies show considerable genetic variation and significant heritability for a wide range of performance traits in aquaculture species under farming conditions, laying the foundation for rapid domestication and performance improvement of specialised aquaculture stocks through modern selection programmes.

Gjedrem and Thodesen listed 21 estimates of selection response for growth rate in 10 aquatic species, averaging 14 per cent per generation, which is more than double the response normally achieved in breeding programs with already highly domesticated terrestrial farm animals. Highly favourable benefit/cost ratios ranging from 8 to 400 are reported for investments in fish selective breeding programmes.

Consequently, the prospects are good for developing high performing and resource efficient domesticated populations and breeds of aquaculture species that may secure the future supply of aquatic animal products and even outperform traditional farm animals in terms of feed conversion efficiency.

The question is why a similar domestication process to that in traditional farm animals has not happened during the history of aquaculture, and what can be done to overcome the lack of progress even today in many farmed species.

In this study, the authors discussed this in terms of biological and technical constraints as well as social and economic conditions, since technology advances alone seem to be insufficient to promote the necessary progress.

The discussion is based on literature studies and on results from interviews with stakeholders, including farmers, breeders and experts from the fish farming industry as well as aquaculture scientists and governmental representatives in Eastern and Southeastern Asia, where most of global aquaculture is located today.

Following an established interdisciplinary approach applied in previous studies, the paper is structured with an initial section reviewing literature and reports on biological and technical constraints followed by a chapter on the perceived needs and interests of actors in Chinese, Malaysian and Vietnamese aquaculture, which is based on the interviews.

In Section 4, the authors discuss the empirical data and semi-structured key-actor interviews to explore the reasons for the slow adoption of selective breeding technology in aquaculture and what can be done to overcome the challenges identified.

The study concludes that most aquaculture species may now be domesticated and improved by selection. However, the adoption of selective breeding in aquaculture is progressing slowly.

The study also tried to identify key issues to address in promoting the development of genetically improved aquaculture stocks. The study involved semi-structured interviews of 34 respondents from different sectors of the aquaculture society in East and Southeast Asia, where 76 per cent of the global aquaculture production is located.

Based on the interviews and literature review, three key factors are identified:

  1. long-term public commitment is often needed for financial support of the breeding nucleus operation (at least during the first five to ten generations of selection);
  2. training at all levels (from government officers and university staff to breeding nucleus and hatchery operators, as well as farmers); and
  3. development of appropriate business models for benefit sharing between the breeding, multiplier and grow-out operators (whether being public, cooperative or private operations).

The public support should be invested in efforts of selective breeding on the most important and highest volume species, which may not be a priority for investment by private breeders due to, for instance, long generation intervals and delays in return to investment.

Further Reading

You can view the full report by clicking here.

September 2015