Experience in raising cold water rainbow trout

(Baonghean) - With the support of the Department of Science and Technology of Nghe An, recently, scientists from the North Central Aquaculture Research Institute have successfully built a project to build a commercial rainbow trout farming model in Na Ngoi commune, Ky Son district - a highland area with a fairly stable source of cold water flowing from streams all year round. The success of this project has also been voted as one of the 10 typical science and technology initiatives of Nghe An in 2011.

The model is deployed in cylindrical composite tanks, cold water is led from a natural waterfall. The size of the fingerlings is from 200 - 230 g/fish, the initial stocking density is 25 - 30 fish/m3. The feed used in the farming process is industrial feed produced by the Aquaculture Research Institute 1 or imported feed.

Rainbow trout pond at Na Ngoi - Ky Son

After 9-10 months of farming, the fish reach a size of about 0.85 - 1.2 kg/fish and are harvested. After 3 experimental farming periods, the model has harvested over 4.3 tons of commercial rainbow trout. The technical indicators achieved are as follows: average survival rate 86.17%; productivity 18.2 kg/m3 of tank; feed conversion ratio (FCR) is 1.6. Currently, the price of commercial rainbow trout sold on the market is from 170,000 - 190,000 VND/kg. The direct accounting results of the model show that, from an investment of about 500 million VND, after 9-10 months of farming, the profit is over 100 million VND.

The profit/investment rate is over 20%. The commercial farming technology process is continuing to be perfected to suit the conditions of Nghe An, along with the perfection of related technologies such as seed production, feed production, etc. to contribute to reducing production costs. Commercial rainbow trout farming in Nghe An promises to become a new profession that brings high economic efficiency to the special climate zone in the West in the near future.

From the model results, some of the following lessons can be drawn:

- Location selection: The farming location should be selected in areas with large areas, relatively convenient transportation, and a regular source of clean water during the farming period. In particular, the water source must have a low temperature, not higher than 230C, and a high dissolved oxygen content (>5mg/l).

- Select and release the fish. Select healthy fish, free from disease, deformities, and natural bright colors. The selected fish should have an average weight of about 200 - 250 g/fish so that the fish can grow quickly and reach commercial size after 9-10 months of rearing. If the fish are still small, they should be reared into larger fish before being put into commercial rearing.

- Farming season: Fish should be released from August to September of the previous year and harvested from April to May of the following year to avoid high temperature periods of the year and limit the impact of the rainy season.

- Fish management and care:

+ Monitor the fish condition daily, feed the fish with the correct portion and time according to the farming process instructions (twice a day).

+ Periodically add vitamin C, minerals, and digestive enzymes to food to increase resistance and help fish grow quickly.

+ Regularly clean the tank and clean tools, create a circular water flow to increase dissolved oxygen in the water in the tank.

+ If you detect signs of fungus or parasitic microorganisms in the fish, you must immediately bathe the fish in 30-35% salt water for 10-15 minutes, or 20-30ppm formalin solution for 5-10 minutes.

+ On rainy days, if the stream is turbid, limit the intake of water from the stream and aerate to ensure the environment is always clean.

- Harvest:

+ When the fish reach commercial size (0.9 - 1.4 kg), the large individuals should be harvested to proactively supply the market. Only collect the entire fish when customers order in large quantities.

Nguyen Thuc Tuan