Post-Harvest Losses of Fish in the Tropics (NRI) Measuring losses (introduction...) The need to assess losses Reducing losses

Post-Harvest Losses of Fish in the Tropics (NRI)

Measuring losses

If an accurate assessment of losses is to be made, information needs to be obtained or collated on:

(i) the fish resources: the main species landed; the quantities involved, and seasonal variations;

(ii) for cured fish, the types of process in use and the amount of fish processed;

(iii) for wet or cured fish, the nature of the distribution system: where the fish is sent and by what transport systems; who is involved in distribution and marketing; how much fish is involved;

(iv) packing systems;

(v) storage facilities; and

(vi) acceptability of the wet or cured fish at various product levels; the level of quality at which the fish becomes unacceptable to particular consumer groups.

After the preliminary appraisal, a detailed study plan can be organized. The basic objectives to, be achieved during loss assessment must he kept in v few at all times. These are:

(i) determination of the type of losses; and

(ii) measurements of the amount and extent of losses.

To know exactly what losses are, one must define carefully what sort of loss is involved. As shown above, there are many different sorts of loss. To assess any of the types, one must measure what losses are in several different places in the country or region in question. This must be done over a period of several years, as any one year may not be typical. This all involves a huge amount of work, and is it worth it?

The types of fish and the products, whether wet and/or cured, to be evaluated, must be specified. The types of loss, whether physical and/or economic, and the number of geographical locations to be sampled must also be considered. Careful thought should be given to this last topic, as small a number of sites w ill not give results which are representative for an area or region, and too large a number will greatly increase the workload involved.

The duration of the survey is critical; seasonal variations will occur, often with handling and processing becoming more difficult during rainy seasons. conditions can also vary from year to year, so although limited base-line data can be obtained from one y car's observations, an effective field survey in loss assessment should last for about three years, and for longer if possible. Background information based on one y ear's appraisal can be up-dated if necessary whilst improvements are actually being implemented.

Only after these data have been evaluated can attention be turned to actual measurement of losses. Loss assessment of fish post-harvest entails troth qualitative and quantitative measurements at every stage of handling or processing, as has been stated above.

Spoilage losses of fresh fish are difficult to assess. In any marketing system which involves perishable produce, traders are prepared to accept a proportion of loss from spoilage, and any trader purchasing a given quantity of fresh fish will be able to estimate how much will have to be discarded instead of sold, although comments to outside observers would need to be treated judiciously. In the case of a regular marketing channel, for instance, the distribution of iced wet fish from landing sites to markets in distant towns, the marketing system will be finely adjusted to minimize losses. Traders are unlikely to be prepared to sustain say 50%Y, losses regularly unless the price of the remaining 50% unspoiled fish compensated for the loss. It is more probable that handling procedures would be improved, or new markets sought in more accessible towns, if losses to the handlers w ere likely to be substantial.

Cured fish losses are difficult even to calculate. The water content changes during, production, and perhaps after wartis if atmospheric moisture is absorbed. The moisture content of the fish must be measured. It each step calculations made to allow a valid comparison of right changes

Wood (1985) has drawn up a detailed schedule for assessing losses ill cured fish which allows for changes ill moisture bone anti salt content. This scheme is reproduced below as Table 3 Unavoidably it is somewhat complicated!

Loss measurement over two consecutive processing stages

If economic losses are being considered in the survey careful evaluation of the price of the fish at every stage in the system will be needed.

Not enough is known vet of what nutrition losts actually occur to make it possibly to the them.

The need to assess losses

The previous section has shown that measuring losses accurately will be a long and complicated process Is it worth the expense involved? Will there be ally benefit from knowing just what losses are?

It is known that substantial losses of fish occur At all stages in the chain from capture to marketing of fresh and cured fish The extent of these losses is rattler academic as what is important is to reduce or prevent the losses, so as to enhance the incomes of those involved in fish production and processing anti to make more food for human consumption available. The instigation of an elaborate and lengthy loss assessment survey will not of itself increase the income of ally fishermen or improve the protein content of the diets of all! impoverished people There is just one set of circumstances when it is necessary to establish the extent of losses.

That is when efforts are to be made to reduce losses Then there will he a need for information on what losses actually occur and when, in order to identify improvements needed in existing processing systems. Careful studies of losses should indicate when improvements most need to be made, and what changes may be required It will then be possible to assess the effect of improved effectiveness methods equipment. In order to monitor the effectiveness of any changes, base--line data are essential. Base-line data clarify and reduce the extent to which losses need to be studied. It is not necessary to know about total losses occurring over a whole region or country, only about those that occur in specific areas where improved methods or equipment are being tested.

Reducing losses

No matter how much or how little information is available on the magnitude of losses the important issue is how to reduce them, to make more food available and, to raise fishing communities income The aspects involved are summarized in Table 4.

Table 4. Action areas for losses of fish post-harvest

Type of loss	Product	Cause of loss	Action
Physical	Cured fish	Fragmentation	Improved curing
Mouldiness	Improved curing
Insects	Pesticides
Spoilage before -	All weather
	processing	processing
Economic
Wet fish	Spoilage fish	Use ice
Improved transport
Nutritional	Improved communications
	Improved! packaging
	Improved sanitation

Source Ames (1990)