Materials and methods The first phase of the phase I production plan was carried out at the Bay Nursery Yard in Xiangshan County, Ningbo, Zhejiang Province. A total of six cages with a volume of 2.25 cubic meters (1.5 meters, 1.5 meters and 1 meter) were used to grow American redfish. The cage is made of a net coat. The top of the cage is a rigid frame and is provided with a shading cover. 0.5 grams of redfish are stocked in six cages at a density of 2,500 fish per cage.
All experimental cages were fed with the American Soybean Association 47/15 (47% protein and 15% fat) seawater fingerling pelleted diet (Table 1). The 47/15 feed used in this trial was formulated by the American Soybean Association and produced by Shanghai Dajiang Aquatic Feed Factory. The feed particle size was 1.5 mm when feeding started. The feeding volume of the six experimental cages was exactly the same and was fed four times a day by satiation and feeding. The first phase of the experiment ended when the fish's average body weight reached 5 grams.
Stage 2 will concentrate the experimental fish from the first stage six-mouth cages and randomly select 4800 tailstocks at a density of 200/m3 in three cages with a volume of 8.0 cubic meters (2m2m2m). . The cage is made of a netting and a frame and is provided with a shading cover and a feeding frame for feeding an extruded pellet feed. The cages are arranged in two rows. The distance between each cage and other cages is the distance of a cage to facilitate water exchange.
American redfish fed the American Soybean Association 47/15 seawater fingerling feed raised from 5.6 grams to 25 grams. When the redfish weighed 25 grams, it was transferred to the American Soybean Association 43/12 marine fish feed (Table 2) and raised until the end of the test. Both feeds are extruded floating pellets. Fish from all experimental cages were fed three times a day by satiation and were fed twice a day after the start of the trial. The feeding amount of each test cage is exactly the same.
The trial management was conducted using the American Soybean Association's small volume high-density cage culture technology. All test cages were sampled once a month on the same day. At the end of the experiment, all fish in the test cages were harvested and the average fish body weight, gross production and net yield, feed coefficient and survival rate were determined.
Results Phase I In the first phase of the trial, redfish were fed a 47/15 feed between June 14 and July 13, 2001 for a total of 30 days. Within 30 days, the redfish was raised from an average body weight of 0.5 g to 5.6 g. The average feed coefficient of 47/15 feed fish fed with six replicate cages was 1.04:1, and the average survival rate was 77.7%.
Two of the two or three 8.0 cubic meters of American redfish experimental cages were tested between July 14 and October 15, 2001 (88 days). The third cage was only fed for 82 days in the same period. Two cages of American redfish raised from 5.6 grams to an average of 92.5 grams in 88 days. The average feed coefficient of two cage fish is 1.31:1, and the average survival rate is
51.3%. The third cage of American redfish grew from 5.6 grams to 88 grams in 82 days. The average feed coefficient was 1.45:1. The average survival rate was 41.9%.
The net income and return on investment of the two net cages on the 88th was RMB 120.4/m3 and 54.3% respectively.
Summary and summary In the first stage of the production plan, the American redfish with a volume of 2.25 cubic meters cage used 47/15 feed, which has better survival rate and feed conversion rate, and its growth performance is good. The second stage of American redfish still maintained a good feed coefficient and growth performance in a cage with a volume of 8 cubic meters, but the survival rate decreased significantly. The poor survival rate is believed to be due to poor water quality and parasitic infections.
A two-stage feed production protocol was tested and 47/15 and 43/12 feeds were used to demonstrate good strategies for breeding American redfish fingerlings. However, producers must be aware that redfish are more sensitive to poor environmental conditions and farmers must choose the areas where the water quality is good.
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