Farming cobia in HDPE round cages in small-scale

On November 16, the delegates from the National Extension Center visited a model of rearing cobia in Norwegian-style HDPE round cages in Vân Phong bay of Vạn Ninh district, Khánh Hoà province.

In the marine farming area of Vân Phong bay, Trần Ngọc Sỹ, owner of the fish cages in Vạn Lương commune of Vạn Ninh district were stocking 1,00 cobia into HDPE round cages, part of the project “Build a model of marine cobia with Norwegian-style HDPE round cages”

Being different from traditional square cages made of bamboo or wood, size 4x4m, the HDPE cages are round-shaped with diameter of 10m and volume of 500m3.

A round cage can bear a load of around 30 adults. Sỹ said that these cages are produced by Vietnam and cost only VND 180 million, half price of the ones imported from Norway.

Cages are clear, helping the fish grow and weigh up well with a survival rate of 80-90%, 10% higher than those reared in traditional cages. Thus, the fish can reach the harvest size of 5kg/pc after seven months. However, due to the Covid-19 pandemic, prices were brought down, approximately VND 120 thousand/kg, thus he decided not to harvest until before Tet Holiday when the market is in high demand and fish prices will increase, promising a high profit.

He shared that there is no difference between farming techniques in HDPE round cages and wooden cages. The HDPE medium-sized cages, which require only two workers, are suitable for every household. Likewise, entirely manual care and harvest are possible without any machines. Remarkably, he could stop worrying about damages driven by storms after shifting to HDPE cage farming.

With these effective cages, Sỹ said, he would replicate more cages for lobster farming.

Director of Khánh Hoà provincial Center of Extension Huỳnh Kim Khánh said that the storm no.12 landed in Khánh Hoà in 2017 and caused devastating damages for aquaculture farmers related to wooden cages in Vân Phong bay.

In the face of the increasingly overwhelming climate, the Center carried out some research and was supported by the National Extension Center when implementing the project “Build a model of marine cobia with Norwegian-style HDPE round cages” in the province.

Accordingly, the project, with six cages, was started in 2020 and ended in 2022. In 2020, the Center installed one cage which produced 5 tons of fish and brought in nearly VND 100 million after ten months of stocking.

In 2021, the Center continued to install two cages and have stocked the fish for seven months. The fish weighed up to 4-5 kg/pc with a high survival rate. In 2022, the Center plans to add three more cages so as to help local farmers in Vân Phong bay and Khánh Hoà province to follow and change wooden cages into HDPE cages.

In Khánh’s opinion, this is the development direction of the National Extension Center as well as Khánh Hoà province in shifting from traditional cages to HDPE cages in the future, planning to complete in 2030 with all wooden cages being replaced with HDPE ones.

So as to fulfil this target, the Khánh Hoà provincial agriculture industry will draw up policies related to cage changes for the environmental landscape assurance in association with tourism and in the track of offshore farming.