The catch in 1969 was 1 270 000 t of which 89 000 t (7 percent) were from fresh water. Thus Thailand ranked eleventh in the world list of nations in terms of total catch and the third after Japan and India in Asia. About 60 percent of the marine catch is estimated to be obtained by trawling.
A large number of different species are caught particularly by trawling and only one type, chub mackerel (Rastrelliger spp.) is worth recording separately. A summary of the types of fish in the marine catch, expressed in percentages is:
| Chub mackerel | 15 |
| Sharks and rays | 12 |
| Molluscs (excl. squid) | 11 |
| Crustacea | 10 |
| Squid | 3 |
| Other | 43 |
Since 1963, after the introduction of trawling into the Gulf of Thailand, the marine catch has been increasing by about 150 000 t a year. The Gulf of Thailand is over fished and this increase has been maintained in the last two or three years only by trawlers fishing off the South Vietnamese coast. This move to fish in more distant waters will be reinforced if fiscal measures which are being considered to reduce the fishing effort in the Gulf are introduced.
At present most trawlers are at sea for less than six days but the trend to distant water fishing will lead to longer voyage periods. This means that handling and icing on-board vessels will have to be carried out efficiently in order to maintain quality and if voyage periods are very long, alternative methods such as superchilling or freezing will have to be introduced.
A summary of the utilization of freshwater fish expressed as percentages of the total freshwater catch is:
| As fresh fish | 54 |
| For production of fermented fish, (pla-ra) | 20 |
| For salting and/or drying | 11 |
| Other uses | 15 |
The utilization of marine fish varies considerably with the type of fish but an overall summary expressed as percentages of the total marine landings is given below:
| As fresh fish | 37 |
| Converted to fish meal | 16 |
| Sold for animal feed without processing | 11 |
| For salting and/or drying | 7 |
| For manufacture of fish sauce, (nam-pla) | 6 |
| Frozen | 3 |
| Other uses | 20 |
The material used for fish meal or direct animal feed comes almost exclusively from the trawl catch as trash fish. About two-thirds of the frozen fish is chub mackerel, almost all the rest being shrimp and squid for export.
Pelagic fish is caught at night by seine net, gill net, etc., iced in bulk in the hold and landed the following morning. This fish is then in excellent condition at the port.
On the trawlers the trash fish portion of the catch is mixed with ice and stored in bulk. The marketable fish is iced in boxes and stowed in the hold. The fish are often forced into the boxes and the boxes are stowed in such a way that the weight of the upper layers is transmitted to the lower ones, thereby losing a good deal of the advantage of boxing to reduce bruising.
The fish boxes and holds are washed down in port with untreated water from the harbour.
Trawled fish are emptied from the boxes into the jetty and sorted for sale. Fish which is to be sent by road or rail is packed into large boxes holding 200 – 300 kg of fish and a similar weight of ice. Three sizes of boxes are in use with external dimensions of 102 × 87 × 77 cm, 86 × 73 × 52 cm and 95 × 64 × 58 cm. The boxes last for an average of ten journeys and rapidly become very dirty as they are not well cleaned after use.
They are transported with their larger dimensions upright and as the journey may take between six and eighteen hours, there is considerable bruising of the fish. Chub mackerel is transported in bulk and mixed with ice in open or insulated lorries.
The traditional methods of fish processing are generally intended as a means of preservation and are carried out on a small scale, cottage industry basis. The preparation of fish sauce, a traditional product, is now carried on in some instances on a factory basis only with regard to size; there is no attempt to modify the method of preparation.
During the last few years shrimp freezing for export has become an important part of the processing industry. As well as this, some vertebrate fish is now being frozen for buffer stocks, most of it chub mackerel.
