The effect of stocking density and diet on the growth and survival of cultured Florida apple snails, Pomacea paludosa

There has been interest in culturing the Florida apple snail, Pomacea paludosa, for stock enhancement purposes in central and south Florida to help promote snail kite (Rostramus sociabilis) recovery. In 2007, Harbor Branch Oceanographic Institute at Florida Atlantic University began to research techniques necessary to culture Florida apple snails at a commercial scale (tens of thousands per year). This article reviews stocking density and diet experiments that have yielded a protocol for large-scale culture of Florida apple snails. The objectives of this research were to determine the stocking density that supports efficient production and to determine whether diet choice affects growth and survival and can improve captive growth rates at higher stocking densities. Juvenile apple snails were stocked at six densities (10, 20, 40, 60, 80, and 100 snails/m²) in recirculating aquaculture systems with a raised substrate. Although growth was faster in the lowest stocking density compared to the highest density during the first month, the difference subsided in the second month, and overall growth rates and final shell lengths were not statistically different. Survival was not affected by density. A second experiment testing higher densities (100, 175, and 250 snails/m²) showed that snails could be stocked as high as 250 snails/m² and confirmed that the lowest density is optimal for first-month growth. An initial diet study examining six diets (romaine lettuce, two combination diets of plant material and catfish chow, and three ingredient-only diets) showed shell length growth rates of 3mm/wk for snails fed the macroalgae Ulva Diet and Catfish Diet (catfish chow only) for two months. In a subsequent experiment, snails stocked at 250 snails/m² and fed the Ulva Diet grew faster than those at the same density fed the Catfish Diet. The greatest growth occurred in snails fed the Ulva Diet and stocked at 100 snails/m². Based on these results, it is recommended that the Florida apple snail be cultured in recirculating aquaculture systems with a raised substrate at 100 snails/m² and an artificial diet of Ulva macroalgae mixed with catfish chow. Snails cultured in this manner are suitable for release into the wild after three months when they reach adult size (25mm) and reproductive maturity.