WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2014 45 (CONTINUED ON PAGE 46) groups. The natural break points for these data were at ratios of 1.29, 1.49, 1.89, 2.65, and 4.02. Jenks Optimization determined that most farms had land to water ratios less than 1.89. Using Jenks Optimization, a ratio <1.29 can be recommended as a standard for improved land use efficiency in pond aquaculture. Land Area Needed to Grow Crops for Feed Ingredients Based on the mean land to water surface area ratio of 1.48, the total global land area devoted to pond aquaculture farms might be around 24.8 million ha. This area underestimates the total land area required for aquaculture because land is needed to grow plants as ingredients included in aquaculture feeds. The area for plant production is difficult to calculate because statistics for aquaculture feed use are not separated by the culture system in which they are used. In addition, not all species are grown only in ponds and not all ponds are supplied with feed. The total land area needed for plant meals was estimated by using average world yield of crop plants2 and typical feed ingredients for some common aquaculture species as suggested by Boyd and Polioudakis (2006); the average land use was 0.274 ha/t feed. Production per unit area of water surface area is reduced in systems that are more intensive or in which there is more than one crop per year. This reasoning does not apply to land requirements for feed. The total amount of land needed for aquaculture feed ingredients can be estimated by making a few assumptions. According to Alltech’s 2013 Global Feed Summary3, 34.4 million t of aquaculture feed were produced globally in 2011. To estimate the total amount of feed produced for pond aquaculture, feed production make precise estimations and data available to the public are often a few years behind. The Ratio of Land Area to Water Surface Area A study was conducted to estimate the total area of land used globally for pond aquaculture: the water surface area of aquaculture ponds plus land area needed to support production in ponds. Data were collected for 100 farms in 26 countries using Google Earth Pro. Ponds ranged from 0.1 to 26 ha. Ponds were divided into five categories, with 20 farms in each category, based on average pond size for farms: <0.5, 0.5-1, 1-5, 5-10 and >10 ha. These farms contained 2,783 individual ponds with a total water surface of 10,923 ha, placed on 14,091 ha of land, or 1.48 ha of land for each hectare of water surface. This sample represents approximately 0.1 percent of the total water surface area of aquaculture ponds globally. Despite the small sample size compared to the total area of aquaculture ponds, the results of the current pond survey should be helpful in framing land use considerations. Data were analyzed based on ratios of farm land area to water surface area. Farms with smaller pond size had a greater average but a more variable land to water surface area ratio. The ratio exponentially decreased as the average pond size on farms increased. The larger the pond the less additional land needed per unit surface area of water. As average pond size increased, the change in the ratio with respect to water surface area decreased, stabilizing at about 1.25 beyond a pond water surface area of 3 ha. The average ratio of total land area to pond water surface area for all farms was 1.48, with a range of 1.08 to 4.02. Jenks Optimization (Goodness of Variance Fit) classified breaks in the data based on distribution of the ratios (Fig. 2). Jenks Optimization reduces variance within groups while maximizing variance between TOP. Farms can be highly concentrated in an area, causing difficulty in discerning boundaries between adjoining farms through satellite imaging, as at this site in Malaysia. Screenshot by Lauren Jescovitch. MIDDLE. These small-pond farms in Asia emphasizes the importance of aquaculture in certain regions. Screenshot by Lauren Jescovitch. BOTTOM. This photo illustrates how land can be developed as an agriculture and aquaculture farm. Photo by Lisa Bott.
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