A food balance sheet presents a comprehensive picture of the pattern of a country's fish supply and its utilization during a specified reference period. The total quantity of fish and fishery products produced in a country added to the total quantity imported and adjusted to any change in stocks minus exports and minus non-food uses, gives the supply available for the indicated reference period.

It is recognized that the final result of a food balance sheet, i.e. the apparent per capita consumption of fish and fishery products, is among the most frequently requested data on fisheries.

Food balance sheets are particularly important for assessing the per capita supply and the degree of self-sufficiency in low-income food-deficit countries.

The compilation of food balance sheet is a statistical exercise which draws together data from various sectors, for example, production and trade. Some uncertainties in this exercise, as well as annual variations in the apparent per capita consumption, should be assumed to be more likely due to problems associated with variable or uncertain conversion factors and inadequate knowledge on stock changes, rather than reflections of changes in the population's consumption habits.

Production: Production figures relate to the total national fish production in terms of live-weight (i.e. the actual ex-water weight at the time of capture or removal from aquatic environment). Production figures cover catch and culture of all fish, crustaceans, molluscs and aquatic organisms, excluding mammals and aquatic plants.

Non-food uses: Includes reduction to meal and oil; utilization of aquatic products for feed and bait; ornamental purposes; withdrawals from markets and any other non-food use of fishery production (e.g. fertilizers, medical uses). Waste is not included. 

Imports: This covers all movements of commercial trade into the country of fish and fishery products. Data on imports include fish caught by foreign fishing vessels and landed in domestic ports. 

Exports: This covers all movements out of the country of fish and fishery products. Data on exports include fish caught by domestic fishing vessels and landed directly in foreign ports. 

Stock variations: This category refers to changes in stocks occurring at all levels between the production and the retail levels. It covers changes in government stocks, in stocks with manufacturers, importers, exporters, other wholesale and retail merchants, transport and storage enterprises. Information on changes in stocks is often not available or incomplete for a number of countries and important commodities. In most instances data on stock variations refer to the minimum required to avoid a negative balance. 

Total food supply: There are various ways of defining supply and, in fact, various concepts are in use. The elements involved are production, imports, exports and changes in stocks (increases or decreases). There is no doubt that production, imports and decreases in stocks are genuine supply elements. Exports and increases in stocks might, however, be considered as utilization elements. Accordingly, the following are possible ways of calculating supply:

1. Production + Imports + Decrease in stocks = Total supply
2. Production + Imports + Changes in stocks (increase or decrease) = Supply available for export and domestic utilization.
3. Production (excluding non-food uses) + Imports - Exports + Changes in stocks (increase or decrease) = Total supply for human consumption. This is the concept used in calculating FAO's Fishery Food Balance Sheets. 

Population: Refers to the present-in-area de facto population, i.e. includes all persons physically present within the geographical boundaries of countries. In general, the population data used are three-year averages of the mid-year estimates published for each country by the Population Division of the UN. In general the population excludes short-term residents (for example, tourists). 

Per capita supply: Data under this category indicate the per capita food fish supplies available for human consumption during a given reference period. It is derived by dividing total food supply by the population.

FAO. 2017. Fishery and Aquaculture Statistics Food Balance Sheets. FAO yearbook/annuaire/anuario 2015. Rome, FAO. 403 pp. (also available at https://www.fao.org/fishery/static/Yearbook/YB2015_CD_Master/navigation/index_content_food_balance_e.htm).