Detailed Explanation of Water Source and Fish Pond Issues in Rainbow Trout Farms

(1) Water source Rainbow trout must be raised in clear flowing water. Groundwater, river water, mountain stream water and seawater can all be used, but the water supply must be abundant in all four seasons, the water temperature suitable, the dissolved oxygen sufficient, and the water clean and pollution-free.

1. Water quality. When selecting a trout farm site, it should as far as possible make use of naturally formed drops in elevation to increase the dissolved oxygen content, and the pH of the water is generally required to be 6-8. 2. Water temperature. The suitable water temperature for raising rainbow trout is 7°C-20°C; below 7°C growth is slow, and above 25°C they gradually die. 3. Water volume. The scale of rainbow trout farming mainly depends on the water supply. The water volume is generally based on the water capacity during the dry season. Under normal circumstances, a water flow of 0.1 cubic meters per second can produce 12-18 tons of marketable rainbow trout per year. (2) Fish ponds For rainbow trout farms using high-density flowing-water pond culture, there are certain requirements for the type, area, structure and arrangement of the fish ponds. 1. Types and sizes of fish ponds. Fish ponds can be divided into four types: fry ponds, fingerling ponds, grow-out ponds and broodstock ponds. The area of each type of pond should be determined according to the water inflow, terrain and purpose. 2. Shape and arrangement of fish ponds. Fry ponds and fingerling ponds are best made of cement or cement rubble structure, while grow-out ponds and broodstock ponds can be earthen ponds or built of cement or stone. The fish ponds used by the Heilongjiang Fisheries Research Institute are mostly rectangular or channel-shaped. A rectangular pond is generally 10 times as long as it is wide; fry ponds are 1-2 m wide, and other ponds are 4-5 m wide. For a water flow of 10 kg per second, ponds of 50-100 sq m can be built. The arrangement of fish ponds generally adopts two methods: parallel and series connection. Before stocking, the fish ponds need to be thoroughly scrubbed and disinfected with quicklime, bleaching powder, etc. At the water inlet, a receiving trough to prevent the entry of miscellaneous fish and an escape-prevention gate made of wire mesh must be installed; foam plastic should be packed tightly between the gate and the gate frame to strictly prevent escape. 3. Reasonable proportion of the area of each type of fish pond. For a rainbow trout farm that carries out the whole process from collecting eggs from broodstock to raising food fish, in order to meet the planned requirements for the number of fish at each stage, the proportion of the area of each type of fish pond to the total area must be reasonable. In view of the differences in water temperature among regions, the cycle for raising food fish may be two years or three years, and the required fish pond area also differs accordingly. 4. Water inlet and drainage system of fish ponds. The size of the water inlet and outlet should be based on factors such as the water flow, flow velocity and the size of the fish pond; it is better to make them appropriately wider, and the drainage outlet should be set at the lowest point. Fish screens must be installed at both the water inlet and outlet to prevent fish from escaping. The mesh size of the fish screens must be determined according to the size of the fish.