Although food security is not generally a major objective of present-day aquaculture production, aquaculture does contribute to overall food supply by increasing the production of popular fish, thus reducing prices and by broadening the opportunities for income and food access (McKinsey, 1998; Sverdrup-Jensen, 1999). Thus aquaculture is thought to be an important mechanism for local food security through reduced vulnerability to uncontrollable natural crashes in aquatic production, improved food availability, improved access to food and more effective food utilization (see Figure 2). At present there is no standard method of measuring and quantifying the contribution of aquaculture to food security. Instead the role of aquaculture can be assessed by looking at its impact on a variety of different aspects of food security using several core indicators, some of which are briefly discussed below.
Figure 2: The interrelation of generic indicators
of food security
(adapted from Saad, 1999; Metz, 2002; Webb et al., 2002)
To be food secure, a population, household, or individual must have access to adequate food at all times. Thus food should be accessible all year round, irrespective of the political or economic situation. Agriculture is particularly vulnerable to environmental shocks such as droughts and floods, and so assessing the reduced susceptibility of aquaculture to natural catastrophes would give an indication of its importance to food security. This could be done by comparing trends in traditional agricultural food production with those from aquaculture under different environmental conditions. Quantifying the cost of losses in the case of inevitable disaster is another way of comparing aquaculture with traditional farming methods. Aquaculture is often a more predictable use of available resources than alternative types of farming (Williams, 1999). Thus the general trends in availability of aquaculture products could also give an indication of the stability of food supply.
The percentage of fish farmers total income received from aquaculture could also be an important measurement of its role in alleviating hunger and poverty, particularly if the amount remains relatively constant throughout the year. If on the contrary fish are only sold during times of economic need, such as when school fees are due, then aquaculture would appear to be more important for financial security than for food security. Coping strategies, such as the foods which are stored or consumed in times of crisis, indicate those foods which are most important for the poor. If these foods are primarily aquaculture products then one could infer that aquaculture is important not only in providing food during the most critical periods, but also in providing cheap and accessible food to those most in need (Ali and Delisle, 1999; Maxwell et al., 1999). The stability of food supply relies on fish production changing in parallel with the human population density in the region, thus this comparison determines whether per caput production is stable and maintains constant food availability.
Individuals require sufficient quantities of appropriate food to be available from domestic production or commercial imports. The relative importance of an increase in aquaculture production could be determined by comparing the per caput food fish supply from aquaculture with that from capture fisheries (Pillay, 1999). The amount of land and water required per quantity of food produced in aquaculture could also be compared to that achieved on land, although species diversity, levels of intensification and the range of products produced may make this evaluation hard. In terms of availability of food supply, the direct contribution of aquaculture to food security could be measured by comparing consumption of aquaculture products to total food consumption measured in terms of energy (kcal/person/year) or protein.
Trade contributes to food availability by reducing supply variability, fostering economic growth and eliminating the gap between production and consumption needs (World Bank, 2003). Data on imports and exports of aquaculture products from sub-Saharan Africa are currently limited but measuring the quantities and value of products traded would be a good indirect indicator of food security. Statistics of products bought and sold at markets could give an indication of aquaculture trade, although some small-scale farmers may not trade at markets. Price fluctuations appear to increase local production, thus assisting rural livelihoods and food security (FAO, 2003a). Thus prices of traded aquaculture products as well as input costs, such as the price of fingerlings, fishmeal and fertilizers, could be used as indicators of the contribution of the technology to food security.
Increasing the supply of fisheries products is not sufficient to improve food security without the assurance of economic, physical and social access to adequate and nutritious food (Kent, 1997; FSIEWS, 2001). Economic access to food occurs when households generate sufficient income to buy food and nations generate foreign exchange to pay for food imports (Sigot, 1998; Williams, 1999). Consumption of fish, often a non-staple food, rises rapidly with income on a percentage basis (Bouis, 2000). One could infer that the higher the proportion of income spent on aquaculture products, the greater the importance of aquaculture in relieving food insecurity since the very poor will buy the most nutritional and calorific food that they can afford. Therefore one method of measuring the relative contribution of aquaculture to food security could be to compare the proportion of income spent on aquaculture products to those spent on other food items as well as on food in general.
Poverty is measured by the percentage of people living in households consuming less than US$1 a day at purchasing power parity (CFS, 2001). The distribution of poverty could be compared with that of aquaculture over time in order to determine whether the extent of poverty decreases in the presence of aquaculture. Aquaculture may provide a primary source of income to many farmers thus ensuring economic access to food (Williams, 1999; Ahmed and Lorica, 2002). The extent of employment revenues, which could be determined through individual surveys, can be used as an indirect measurement of the contribution of aquaculture to food security. A comparison of direct revenues generated from aquaculture to the value of items in the consumption basket can also give an indication of the relative indirect contribution of aquaculture products to food security.
Individuals must be able to get to food supplies and so increasing the physical access of the poor to productive resources may be a more reliable guarantee of food security than increasing purchasing power (Ahmed, 1999). The supply of fish in landlocked nations may be limited by poor infrastructure or storage facilities and so the accessibility of dried fish may be important in areas where fresh and frozen products are not easily available (Thilstead and Roos, 1999). Important aspects therefore include the distance from food distribution sites and the types of products available in nearby markets (FSIEWS, 2001). Commercial aquaculture may primarily respond to the market demand of the rich rather than improving food security (Kent, 1987) and so indirect indicators, such as the literacy level, dependency ratio and gender of fish farmers, could be used to determine what type of household benefits from aquaculture (Webb, Coates and Houser, 2002).
Social access to food requires supplies to be equitably available to people of all cultures and beliefs. Thus studies on the attitude towards aquaculture would be useful to assess the acceptability of the technology by different classes and religions (Pérez-Sánchez and Muir, 2003). Equitable social access to aquaculture could also be determined by assessing which aquaculture products are acceptable in different societies and whether there are any gender differences.
The effective utilization of food is an important aspect of food security and relies on sufficient energy consumption and a varied diet to provide required micronutrients. Inadequate diets are likely to occur primarily in terms of quality rather than quantity as poor people will initially strive to fill their stomachs to meet their energy needs and the cheapest foods have the poorest quality (Allen, 1994). At a global level there has been significant progress in raising food consumption per person, and diets have shifted away from staples such as roots and tubers towards livestock products and vegetable oils (Bruinsma, 2003). The energetic contribution of aquaculture products could be assessed in terms of calorific importance (Christiaensen and Boisvert, 2000). However people do not live on carbohydrate sources alone and a high percentage of energy derived from starchy staples, such as cereals, roots and tubers, indicates a relatively poor diet in terms of diversity. Low dietary diversity suggests that people are deficient in many of the micronutrients needed for good health (CFS, 2001). Which species of fish is farmed is therefore a potentially useful indication of aquacultures role in alleviating hunger, as fish have different amounts of flesh, calcium-rich bones, vitamins and fatty acids (Prein and Ahmed, 2000). Protein should provide between 10 and 12 percent of energy intake while the recommended amount of fats is between 15 and 30 percent (FSIEWS, 2001). Thus in addition to assessing the percentage of energy in the diet derived from cereals, the proportion of protein derived from aquaculture products should also be considered. Animal protein supply could also be determined across different regions to indicate where aquaculture gives the greatest benefit (Tacon, 2003).
Several studies have used anthropometry, the use of human body measurements to obtain information about nutritional status, to show that improved nutrition is linked to increased productivity and wages (Strauss, 1986; Strauss and Thomas, 1998; Croppenstedt and Muller, 2000; Bruinsma, 2003). Life expectancy is lowest in countries with the highest prevalence of undernourishment because hunger and malnutrition shorten lives. A high incidence of under-five mortality, wasting, undernourishment and stunting can also indicate food insecurity, although other factors such as disease prevalence and health care are also important (Maxwell et al., 1999; Bruinsma, 2003). Although improved life expectancy, growth, fertility and reduced mortality rates are useful indicators of an improving food situation, neither these statistics nor those derived from anthropometry can be attributed solely to the presence or absence of aquaculture.