Fish trapping at a fast-flowing brook in Vietnam

Trapping fish in bamboo traps in Southeast Asia is normally a static affair. These fishing traps will be used in still waters with or without bait inside and checked at least once daily. It was a new experience, to see somebody trapping fish with bamboo traps on the go in fast-flowing waters.

Sa Pa is a town in the far north of Vietnam, within the Hoang Lien So mountains. Its elevation is 1600 m above sea level. Fish trapping, which I observed, was done in the Cau May brook. This brook was on average about 20 meters wide and fast-flowing. The whole brook was strewn with rounded boulders of various sizes. Possible species of fish to be caught can be seen here. In the holding basket of one of the fishermen I only saw loaches (Schistura sp.).

What does the fishing trap look like?

Trapping baskets are about one meter long and consist of a wide opening cone. This opening cone extends into the catch room. The neck area between the opening cone and the catch room is quite slim. Therefore the basket can be held by one hand in this area. At the back end of the catch room, there is an extended opening hole. This will be closed with green, broad leaves. A string is attached outside the basket for easier carrying on land.

Fishing technique by flushing out fish underneath stones

Fishing is done in such a way, that fishermen are looking for deeper spots in the river. In these spots, the basket cone can be completely submerged. It will either be held temporarily in place underwater by a stone squeezed in between stones or held down by the fishing partner. Thereafter the fisherman disturbs the surrounding area by either his feet or hand. Or he is using an iron crowbar to lift bigger stones around the trap. This will flush out fish, which will try to find a new hiding place. This hiding place could also be the bamboo basket. As the water is streaming through the woven basket and it is slightly dimmed there, it will be regarded by fish as a likely hiding place.

Fish can remember occurrences and places over many months long. And it is not correct that fish have a memory time span of only 9 seconds, as believed in older days. But the river changes constantly due to its movements. Therefore, a new natural material that has been there in place will be seen as a natural occurrence by fish.

Fishing technique by constricting fish escape routes

Another catching technique with fishing traps is by walking the river upstream and holding down the trapping basket. Especially at constrictions after deeper passageways and sideward of the fisherman. Fish will sense vibrations via the lateral line and see the fisherman below and above the water. And will try to escape from them. The best escape route is the fastest escape route. They therefore swim with the current downstream. Upstream in fast-flowing water, they are considerably slower and need far more energy. And if there is a constriction after the passageway, they will take that route. Especially if the water is flowing freely through the basket and the area is a bit shaded.

Fish caught by one of these two tactics by fishing traps will be offloaded live into the holding basket of the fisherman. They however will succumb after some time due to lack of oxygen.

Lessons learned from fish trapping on the go near Sa Pa

  • Trapping fish in baskets in fast-flowing waters seems to be easy. But is hard work as the water has to be read constantly. And often a crowbar has to be used for lifting stones
  • The water is cold, and the stones are slippery. It is not very pleasant to walk in the water for an extended time.
  • Fish caught this way are relatively small. Mainly about 12–15 cm long, but as in this specific area, no piscivorous animals are occurring, fish are plenty. The catch of two hours of fishing is enough for a meal for the family.

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