The stake trap or fish corral (No sao) is a low-selective fishing gear, which means that the gear is not able to let the juvenile escape from the traps. Nets currently used for stake traps capture all sizes of fishes, including juveniles, thus interrupting their natural life cycles.

The major reason for this low-selective nature of stake traps is the small mesh size of the net used (4-6 mm). The IMOLA study on fishing capacity found that most of the catch in stake traps was smaller than the legal size, confirming the low selectivity of this fishing gear.

One of the natural roles of the Tam Giang Cau Hai Lagoon, like other lagoons, is that of a nursery ground. Many species use the lagoon as their ideal habitat for the first stage of their life. Giving this fact, existance of approximately 1400 units of this non-selective fishing gear in the lagoon would pose a tremendous impacts on the fish population in the lagoon.

Another problem caused by the small mesh size is the obstruction of the water current inside and around the gear. Smaller mesh nets reduce the water exchange in the lagoon and increase the sedimentation rate, leading to ecological problems such as low oxygen saturation, build-up of organic pollutants, and eventually the reduction of the carrying capacity of the lagoon.

Management plans for stake traps has been prepared by several District People's Committees (DPCs) and the Department of Agriculture and Rural Development (DARD) of Thua Thien Hue Province. However, the issue of suitable mesh sizes for the gear is still controversial among stakeholders -- neither density nor size of the stake traps has been worked out.

With this background, the IMOLA Project has conducted an experimental study on the effects of different mesh sizes for stake traps to understand their impacts on fish population as well as the livelihoods of the fisherfolk.

For more detail, please refer to the Increasing the Mesh Size at Traps of Fish Corrals in the Cau Hai Lagoon (pdf).