The technique of culturing rainbow trout with cage in the bottom water of the reservoir

From January, 2005 to July, 2006, we carried out small-volume cage culture experiment of rainbow trout under Zhangwu reservoir power station in Anyang City, Henan Province, using reservoir bottom water, and achieved good results. The test is summarized as follows:

I. MATERIALS AND METHODS

1. Zhangwu Reservoir is a hilly medium reservoir with fresh water, rich dissolved oxygen, pH 7.2 ~7.6, average transparency 76 cm in summer and 150~200 cm in winter. The net cage is set in the return pond under the power station, the transparency is 150cm, the pH is 7.4, the dissolved oxygen is 8 - 10mg/L, the water temperature is 13 - 15 DEG C in winter, the water temperature is 17 - 19 DEG C in summer, and the flow velocity is 0.47m/s.

2. The net cage structure and setting are sewed by double-layer 5×3 node polyethylene mesh, the mesh of negative seedling box is 0.5cm, the net cage specification is 1m × 1m, the mesh of adult fish box is 2.5cm, the net cage specification is 2m × 2m × 2m, the four sides of the net cage are made of bamboo as frame, foam plastic and oil drum as float, bricks as sink, so that the net cage can be completely extended in water. 10 days before the fingerling stocking, the net cage will be put into water to soften it and attach some attachments to reduce the scratch when the fingerling enters the box.

3. Fish stocking 26 kg rainbow trout fry were purchased from Huairou, Beijing in March 2005, specification 4.2 g/fish. Disinfect fingerlings with 3%~5% saline for 10 minutes before stocking.

4. feeding management

(1) Feed feeding: Rainbow trout soaked in warm water shall be fed on the third day after fry are put into the box. The specific method is to soak the feed in warm water at 40℃ for 20 minutes before feeding, and the ratio of water to feed is 1:1. 3 times a day, 9:00~10:00 in the morning, 12:30~13:30 in the afternoon and 16:00~17:00 in the afternoon. When the fry grow to about 15 cm, they are fed with rainbow trout adult feed three times a day, 8:00~9:00 in the morning, 12:00~13:00 in the afternoon and 17:00~18:00 in the afternoon, each time 7%~10% of the fish body. Specially assigned personnel shall be responsible for feeding, adhere to the "four fixed" feeding, and flexibly control the feeding amount according to the weather, water temperature and negative feeding conditions.

(2) Daily management: special personnel are responsible for management, 24 hours a day observation, keep a log. Clean the cage once a week to ensure the convection of water inside and outside the cage. Check the cage regularly for damage to prevent fish from escaping. When the weather is hottest in July, August and September, black plastic nets are set up above the net cage to block sunlight, so as to avoid direct sunlight on the water surface. The water temperature is too high, which affects the feeding growth.

(3) Fish disease prevention and control: sprinkle and disinfect the whole box with "bromochlorohydantoin" once every half month. The method is twice a day, 100 grams each time,"bromochlorohydantoin" dissolved in water after the whole box evenly sprinkled, for 3 days. Antibiotic baits were fed once a month for 6 days. The above measures have significant preventive effect, coupled with low water temperature and fast flow rate, no fish disease occurred during the breeding period.

II. Results

Sold in July 2006. A total of 2795 kg rainbow trout were harvested, with an average specification of 650 g/fish. The price was 42 yuan/kg and the output value was 116390 yuan. The total expenditure is 66364 yuan, including 5000 yuan for seed, 53664 yuan for feed, 1300 yuan for fishing medicine, 5000 yuan for personnel salary and 1400 yuan for net cage depreciation. The net profit was 50026 yuan, and the input-output ratio was 1: 1.75.

III. Discussion and analysis

1. Net cage setting Net cage is set in the area where the flow rate is slower, the temperature is lower and the direct sunlight is not received, so as to facilitate the feeding and growth of fish. In order to prevent high temperatures in summer, a sunshade is set up above the net cage.

2. Fish species stocking and survival rate Rainbow trout breeding should enlarge the specifications of fish species and be raised in grades, that is, with the growth of fish bodies, the stocking density is 1500 fish fry/cubic meter, 300 fish species/cubic meter, and 60 fish/cubic meter. In our breeding process, because of sufficient feed and good water quality conditions, the breeding density is relatively large. As for the specific data of stocking density, it depends on specific conditions. Our culture is low in water temperature, fast in flow rate, full of dissolved oxygen and less in disease, so the survival rate is high, reaching 86%.

3. Feed feeding and feed coefficient Rainbow trout feeding fierce, large appetite, so according to 7%~10% of body weight to feed, feeding time interval should be longer, in addition to the last meal of feeding accounted for 50% of the day. Every time you feed 80% full, you should pay attention to the palatability of the feed. When fry are young, they are soaked in water, and then powder, small particles and large particles are used as fish grow. Use rainbow trout special feed, nutrition comprehensive, fast growth.