Introduction

Fish is one of the most important food staples on the planet. Its flesh is a source of top quality protein, and for many in the less developed parts of the world it represents a significant proportion of the animal protein in their diet, either as fresh fish or cured in a variety of ways, such as smoking, salting and drying. Fish can also be seen as a renewable natural resource, provided that the seas and lakes are not overfished. Unfortunately, however, fish is one of the most perishable of all staple commodities, and in the tropical climates of most developing countries it will become unfit for human consumption within about one day of capture, unless it is subjected to some form of processing. Even after the fish has been processed, particularly if traditional methods have been used, the fish is still subject to many forms of loss and spoilage.

For the past twenty or so years, there has been increased global emphasis on fish production by traditional capture fisheries. World fish production rose from 40 million tonnes per annum in 1960 to 70 million tonnes per annum in 1970. Since 1970 the rate of increase in landings has slowed down, rising by about one million tonnes per annum to a provisional figure of just under 100 million tonnes per annum in 1989. This levelling off is because stocks of the more accessible fish popular for human food are being fully exploited. In some areas, catches are above the sustainable level, putting the future of the fishery in jeopardy.

The demand for fish is increasing. Even a small increase in living standards in many developing countries leads to a greater requirement for fish. The health conscious, more developed countries are becoming increasingly aware of the high nutritional quality of fish.

The Food and Agriculture Organization of the United Nations (FAO) has estimated that by the year 2000 the total world demand for fish will be about 120 million tonnes per year. This cannot be met by landings from existing capture fisheries and aquaculture. If the demand is to be satisfied then other solutions will have to be found. Aquaculture can play a greater role in providing fish for human consumption, but so far it provides only 10% of fish production. The major emphasis will need to be on the improved utilization of marine fisheries. This will entail increasing landings by the exploitation of less popular and lower value conventional meso-pelagic fish types. It will also become increasingly important to ensure that fish once caught is fully and efficiently utilized.

The global pattern of fish utilization has changed markedly since about 1950, the proportion of fresh and cured fish falling, and that for frozen and canned fish increasing. Despite this trend, fresh and cured fish remain the most important items in the domestic markets of the developing world, and both fresh and cured fish are subject to high post-harvest losses; that is, a significantly smaller quantity of fish reaches the consumer than was originally caught.

It is difficult to estimate the extent of these losses, as very few quantitative studies have been carried out. However it is clear that post-harvest losses in the small-scale fisheries sector are among the highest for all the commodities in the entire food production system.

Post-harvest losses of fish are of various types. The most obvious are the losses of material, or physical losses, caused by, for example, poor handling and processing, or the discarding of by-catch. There are also economic losses which occur when spoilage of wet fish causes a reduction in its value or when there is a need to reprocess cured fish, increasing the cost to the processor. Traditional processing methods can cause a reduction in nutrient availability, leading to nutritional loss. Various reviews have included estimates of total losses, and typical figures are given in Table 1 below.

Table 1. Under-utilization of conventional fish stocks

Type of fish	Form of loss	Million tonnes/year
Wet fish	Post-harvest losses	2
Cured fish	Post-harvest losses	3
By-catch	Discarded at sea	5-20
Pelagic fish	Used for fish-meal	20
Pelagic fish	Under-exploited	20

This publication examines these three types of loss in some detail, describes ways of overcoming losses, and gives some examples of means of reducing losses.