54 MARCH 2017 • WORLD AQUACULTURE • WWW.WAS.ORG production obtained at the end of the culture period with both feeds. The same survival (70 percent), harvest weight (20 g) and culture period (100 days) were assumed to be able to observe the impact that a reduction in the FCR on the efficiency of the productive model. Using data from Table 4 as an example, another way of calculating the fixed cost is: Cost of production = Cost of food + other costs of production = $ 2313 + $ 2000 = $ 4313 The exercise shows that a production model oriented to reduce the FCR by <20 percent permits improvement of PI/ha per d by 6 percent. To obtain a higher PI/ha per d one should be oriented to increase weekly growth and keep survival high. Productive Efficiency Indicator (PEI) The Productive Efficiency Index (PEI) is an indicator that expresses productive efficiency. It allows comparison of productive models used or intended to be used. The PEI does not have units; it is expressed from 0 to 1. PEI = (B × WG / FCR × FP) / 10,000 Where PEI = Productive Efficiency Index. B = Biomass, WG = Weight gain, FCR = Feed Conversion Rate, and FP = Feed Price Automatic feeding is the new tendency for feed management in Ecuador and Peru. FCR reduction is accomplished by multiple daily doses and supply during the period of greatest feed demand from the shrimp, making an impact on improving productive indicators. The productive efficiency has a direct relationship with a higher weekly growth of shrimp, because it generates the greatest positive impact on the productive indicators. Data from 2768 harvested ponds in Guayas, Ecuador were analyzed. Irrespective of the type of stocking, stocking density or any other productive variable, a higher PEI is obtained when weekly TABLE 3. An exercise on the effect of the duration of the culture period on PI/ha per d. Brand A Brand B Feed price (US$/kg) $1.10 $1.00 Type of stocking Transfer Transfer Stocking density (shrimp/m2) 10 10 Days of culture 100 120 Average weight increase (g/wk) 1.40 1.17 Average weight at harvest (g) 20 20 Survival rate (%) 70 70 Harvest biomass (lb/ha) 3,084 3,084 FCR 1.5 1.5 Fixed Cost (US$/ha per d) $20 $20 Total Fixed Cost (US$/ha) $2,000 $2,400 Feed Cost (US$/ha) $2,313 $2,103 Total Cost (US$/ha) $4,313 $4,503 Cost of shrimp (US$/lb) $1.40 $1.46 Final sales price (US$/lb) $2.60 $2.60 Total Income (US$/ha) $8,018 $8,018 Productive Index (PI) $3,705 $3,515 PI/ha per d $34 $27 TABLE 4. An exercise on the effect of feed quality and price on PI/ha per d. Brand A Brand B Feed price (US$/kg) $1.10 $1.00 Type of Stocking Transfer Transfera Stocking Density (shrimp/m2) 10 10 Days of culture 100 100 Average Weight Increase (g/wk) 1.40 1.40 Average weight at harvest (g) 20 20 Survival rate (%) 70 70 Harvest Biomass (pounds/ha) 3,084 3,084 FCR 1.5 1.8 Fixed Cost (US$/ha per d) $20 $20 Total Fixed Cost (US$/ha) $2,000 $2,000 Feed Cost (US$/ha) $2,313 $2,523 Total Cost (US$/ha) $4,313 $4,523 Cost of shrimp (US$/lb) $1.40 $1.47 Final sales price (US$/lb) $2.60 $2.60 Total income (US$/ha) $8,018 $8,018 Productive Index (PI) $3,705 $3,495 PI/ha per d $34 $32 TABLE 5. An exercise on the effect of weekly growth rate on productivity indicators. Weekly Growth (g) PI/ha per d ($) Productive Efficiency Indicator (PEI) n 0.5 – 1.0 7.15 0.13 532 1.01 – 1.10 15.09 0.17 359 1.11 – 1.20 22.83 0.21 500 1.21 – 1.30 28.06 0.24 459 1.31 – 1.40 32.13 0.27 320 1.41 – 1.50 40.95 0.32 227 1.51 – 1.60 46.41 0.36 166 1.61 – 2.0 52.07 0.41 181 > 2.0 65.15 0.57 24 Total 2768 n = data of harvested ponds of shrimp farms in Guayas, Ecuador.
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