Trawl Fishing

      Trawls are one of the most important types of fishing gear in Vietnam . The fishing production from trawling is about 40% of the total catch. Trawls have been used in Vietnam for a long time. In the early years, fishermen used two sailing boats to drag one trawl. The nets were made of cotton and the buoys were made of wood with a rectangular or hydrodynamic shape. The fishing grounds were mainly coastal areas with depths of less than 20 m.

     Up to the year 1957, with the technical assistance of the Democratic Republic of Germany, four trawlers of 90 Hp were used with two-scam trawl nets in the Gulf of Tonkin .

    During the year 1958, the People's Republic of China supplied Vietnam with 15 otter-board trawlers with an engine capacity of 250 Hp, each. These steel-hulled vessels were 28 m long and operated very successfully in Vietnamese waters. In 1976, Norway provided Vietnam with four steel-hulled otter-board trawlers of 600 Hp, each. The four-scam, high opening trawl nets were used in these vessels for fishing in the Gulf of Tonkin .

     Up to the present, trawl fishery has developed to over 20,000 units. However, because of natural conditions in the fishing grounds, trawl fishery only developed in the Northern and Southern provinces of Vietnam .

    At present, most trawls used in Vietnam are types of two-scam, only in recent years, fishermen in the Southern provinces have used some models of four-seam trawl net with a high opening.

    Because of the smooth seabed, bottom sediment is sand-mud, so most of trawls use a “soft ground rope”. This means that there is little use made of bobbins, iron discs or rubber discs, thus the ground rope directly contacts the bottom, and fish cannot escape because of the ground rope. Besides, the “soft ground rope” reduces the hydro-resistance of the trawl while towing. The otter boards have a rectangular, oval or V-letter shape.

Today, the trawl fisheries have some main groups as follows:

      - Most of the trawlers often use the pair trawl method and are equipped with a large engine capacity of 135-500 Hp per boat. The towing speed is 3.5-4 miles per hour. However, this speed is slower than that needed for successful fishing.

     - The shrimp trawlers often use the otter trawl. One boat can tow one, two or sometimes up to 18 trawls. For horizontal opening trawls, they can use two fishing methods: otter-board trawls and beam-trawls. The fishing grounds of the shrimp trawls are only in the coastal areas where the depth is less than 30 m.

     From 1997 until the present, the big mesh size trawls have been imported from China . The characteristics of the sizes and meshes of these trawls are larger than those of ordinary trawls (see Table 7 ). The target species of the Chinese trawls are sardine, which are 80-90% of the total catch. Thus, although the total catch of the trawl is very high, the total income is low. On the other hand, this trawl only operates successfully in the coastal areas with a water depth of less than 30m, however it is not good for living resources in this area and causes conflict with small scale fisheries.

Table 7: The main parameters of Chinese and Vietnamese trawls for pair trawlers that have 300Hp/unit.

Fishing Gear and Methods

Trawl fishing in Vietnam can be classified into four types:

- Beam trawl

- Bottom otter board trawl

- Bottom otter board trawl with booms

- Bottom pair trawl