WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2019 39 Furthermore, survival for automatic feeding (acoustic, timer and multi-feeding) is much higher (between 61 and 66 percent) compared to traditional feeding (56 percent), where feed is applied by broadcast feeding <6 times/d. No significant differences were observed in growth rate because it was not known in detail the management of automatic feeding and the greater survival that had been achieved; therefore, it is identified as an important improvement opportunity with this new feeding technique. The greater biomass (1,6341,721 kg/ha) corresponds to the greater survival achieved of shrimp ponds with automatic feeding and multi-feeding management (1,852 kg/ha), considering that the density was higher. In ponds with broadcast feeding, harvest biomass was 1,379 kg/ha. Zones and Feeding Frequency The ethology of the shrimp requires us to know the eating behavior. Shrimp consume feed when they have the appetite and that does not necessarily coincide with the timing of feeding. The correct frequency of feeding influences growth rate and FCR. The effect of the form of feeding in the model of multi-feeding several times a day and ad libitum is directly related to shrimp growth. The more times per day a shrimp feeds, the greater the chances of achieving a greater growth rate and therefore fewer days of culture (Fig. 1). Automatic feeders disperse feed in a range of action that is specific to each brand of automatic feeder. The diameter of the feeding zone varies according to the brand of automatic feeding equipment. It can be up to 30 m, but the greatest amount of feed tends to be concentrated between 4-10 m and between 14-20 m of the trigger center of the automatic feeder. Results from Honduras and Nicaragua The first experiences of automatic feeding implementation on shrimp farms in Honduras and Nicaragua are described in Table 2. The average size of grow-out ponds in Honduras and Nicaragua is 10 ha. The first results have given way to the rapid implementation of this strategy of improving feeding efficiency in the Central American shrimp industry. Even with higher stocking density (+40 percent), when implementing automatic feeding, a greater weekly growth rate (+33 percent), greater survival (+54 percent), lower FCR (-13 percent) and above all lower production cost (-39 percent). When automatic feeding is installed, shrimp farmers tend to increase stocking density. At one shrimp farm (A) in Nicaragua, a production model using conventional feeding in 2016 was compared with one using automatic feeding and a 40 percent higher density (14/m2) in 2017, both with transfer of juveniles from a nursery. In comparison with conventional feeding, automatic feeding resulted in a 33 percent increase in growth rate (1.55 vs 1.16 g/wk). Shrimp reached 21 g of weight in 93 days of culture with automatic feeding, compared to 17 g achieved in 100 days of culture with conventional broadcast feeding. Survival increased considerably from 47 percent to 72 percent and FCR reduced from 1.5 to 1.3. In economic terms, this represents a reduction of 39 percent in shrimp production cost from US$1.98/lb to US$1.21/lb. With similar stocking density, when implementing automatic feeding, a greater growth rate (+17 percent), survival (+38 percent) and harvest biomass (+38 percent), and lower cost of shrimp production pound (-9 percent) (Table 3). Due to the recent little experience in automatic feeding management it is likely that it was caused by under-feeding, because a lower survival was assumed and growth rate could not be enhanced as expected. With greater stocking density (+12 percent), when implementing automatic feeding, a greater growth rate (+23 percent), survival (+22 percent) and harvest biomass (+67 percent), and lower production cost (-24 percent) (Table 4). Results from Ecuador In Ecuador, studies assessed feeding methods with three methods of stocking: direct stocking, raceways and nurseries. The average size of grow-out ponds in Ecuador is 8 ha. Direct stocking is usually done by stocking shrimp larvae from hatcheries at the PL12 stage directly into grow-out ponds. During the first month of cultivation, shrimp are fed by broadcasting feed from pond embankments. During this time, predetermined feeding (CONTINUED ON PAGE 41) FIGURE 1. The relationship between feeding frequency and shrimp weight (g). Source: Skretting Validation Station, Ecuador, 2016, 2017. LEFT and RIGHT: Timer feeders installed in shrimp ponds in Ecuador. In photo on left, note stick emerging from water near feeder for a feeding tray to evaluate the feeding protocol. Multi-ration 2 times/d 1 time/d
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