Polyculture of Pacific white shrimp, Litopenaeus vannamei, giant oyster, Crassostrea gigas and black clam, Chione fluctifraga in ponds in Sonora, Mexico

The feasibility of a polyculture of Pacific white shrimp, Litopenaeus vannamei, giant oyster, Crassostrea gigas, and black clam, Chione fluctifraga in earthen ponds, and its effect on water quality and production parameters, was assessed in a nine-months experimental study, conducted in Sonora Northwestern Mexico. Shrimp was stocked for two crops and mollusks for a single crop during the study. Two oyster densities (10 and 16/m2), two clam densities (8 and 10/m2) and one shrimp density (30/m2) were evaluated in the experiment. Total ammonium nitrogen and chlorophyll-a were significantly lower in the ponds with the highest combined density of mollusks. During the first crop, shrimp reached 12.6 to 14.88 g in 19 weeks from postlarvae of 10 days age (around 0.002 g), with a survival ranging from 48.3% to 63.1% and a yield from 1866 to 2665 kg/ha. During the second crop, the gain in weight, survival and yield of shrimp ranged from 12.23 to 13.26 g, 61.9% to 67.3%, and 2271 to 2677 kg/ha, respectively. Oyster mean weight increased between 40.2 to 50.1 g in 6 months, with a poor survival of 10.7% to 16.2% and a yield of 746 to 1014 kg/ha. Clams grew in a range from 13.3 to 14.0 g in the same period, with a survival of 45.5% to 50.2% and a yield of 617 to 793 kg/ha. It may be concluded that polyculture of these three species seems to be feasible and that the presence of mollusks in the ponds might not have an adverse but a beneficial effect on the productive performance of shrimp. Crassostrea gigas showed not to be a good prospect for this polyculture conditions but C. fluctifraga could be a good candidate.