According to the Food & Agriculture Organization of the United Nations (FAO), nearly half the fish consumed worldwide are raised on fish farms, rather than caught in the wild. In 1980 just 9% of human fish consumption came from aquaculture; today, that figure exceeds 43% - over 45 million tonnes a year.
Globally, consumer demand for fish continues to climb, especially in affluent, developed nations, whilst capture levels of wild fish have remained roughly stable since the mid-1980s. There is, according to the FAO, very little chance of significant increase beyond current catch levels; indeed, with almost three quarters of the world's fisheries either fully or over exploited, catch levels could easily fall, and it is therefore inevitable that aquaculture will be called on to meet a significant proportion of our rapidly rising demands.
It comes as no surprise, then, to learn that fish farming is the world's fastest growing food sector, with many countries focusing on high-value carnivorous fish such salmon or trout. However, the farming of these species can generate significant environmental impacts as they often depend on wild caught fish as a food source. This, in turn, presents an additional threat to wild stocks.
A possible alternative is to grow omnivorous species that occupy lower levels of the food chain and which might therefore require lower energy inputs to produce fish protein. One such species is the Common or European carp (Cyprinus carpio). In fact more carp are farmed worldwide than any other group of fish, with the bulk of this economic activity taking place in Asia and Europe.
Of all our aquaculture systems, carp farming has the longest history. The knowledge gained over centuries of traditional pond culture has largely provided the basis for commercial fish production, and the energy efficiency of this sector has recently been examined by researches at the Central Institute of Freshwater Aquacul ture (CIFA).
The principal raw material of any intensive agriculture system is fossil fuel, and, with international fuel prices rising unpredictably, increasing attention being paid to the energy input costs associated with different food production systems, with particular attention being paid to aquaculture.
Researchers at CIFA examined a wide range of carp farming techniques and considered how much energy was required to produce one gram of finished product. They then examined how the energy efficiency of these carp farming systems compared to the most ruthlessly efficient (in energy terms) of our intensive live-stocking systems, i.e. large-scale commercial egg production.
Their results showed that the simplest, most sustainable carp production systems (artificial ponds with additional energy inputs largely limited to the addition of natural fertilizers) required between 109 and 132 Kilo Joules of energy input for every gram of protein output (KJ/g).
Where carp production was intensified by the addition of large amounts of artificial fertilizer and commercial feed, the subsequent energy requirements ranged from 205 KJ/g to 418 KJ/g, with most of the variation being caused by the levels of supplementary feeding being applied and the high energy costs associated with the production of high protein commercial fish food.
Where high protein feed was supplemented with artificial aeration (to allow commercial stocking densities) energy costs climbed to around 470KJ/g, but this still compares favorably with the energy requirements of intensive egg and poultry production that, typically, will have energy inputs starting at around 552 KJ for 1 g of protein.
So, can large-scale carp aquaculture deliver? Should sport-oriented carp farms consider diversifying into food production? Well, the jury is still out, according to the FAO. Aquaculture certainly has the potential to cover the gap between supply and demand, but t here are also significant forces that could pull production in the opposite direction.
Aquaculture has been experiencing a global boom since the mid-1980s, sustaining a growth rate of around 8% per year (with the notable exception of sub-Saharan Africa). Although this sustained expansion is impressive, the FAO is concerned that momentum could taper off if governments and development agencies don't adjust their policies to respond to challenges that threaten to dampen the sector's future growth. One such bottleneck, argue CIFA, is a lack of investment capital for producers in the developing world. However, the greatest restraints are likely to be a shortage of land and, in particular, a shortage of reliable freshwater supplies.
Despite these problems, the farming of carp (and other omnivorous fish species) is likely to continue its expansion, and many of us who might previously have considered this species in terms of sport rather than food may soon be revising th at opinion.
Full details of CIFA's research ("Energy Cost in Carp Farming Systems", Olah, J & Sinha, V.R.P.) can be found at http://www.cifa.in.