Influencia del drenaje de estanques de cultivo de camarón sobre las características físicas y químicas de las aguas marinas adyacentes

Abstract

Monhly sampling was performed during August 1993 to October 1996, inside and outside three tidal ponds used for shrimp culture. Our aim was to identify if the culture conditions could influence the surrounding waters and induce some adverse impact. Temperature, dissolved oxygen, salinity, sulfate, nitrate, nitrite, inorganic and organic phosphorous variables were measured. The sampling period comprised three stages of pounds development: a) Initial stage (0% of water exchange, no shrimp culture) characterized by high salinity (80%) and sulfate (6 g l-1) values, and high nitrite variability; b) Intermediate stage (30% of water exchange, shrimps fed with pelleted food), where a bance between external and internal variables was reached. It was obtained a yield of 450 kg ha-1. c) Final stage (itroducing paddlewheel aerators and fertilizing the ponds with superphosphate and urea), showing an increase in dissolved oxygen, nitrates and inorganic phosphorous variability, either inside and outside the ponds, and increase in organic phosphorous inside the ponds. During this final stage a yield of 1500 kg ha-1 was obtained. Te organic matter input by the pelleted food, induced microalge growth and shrimp metabolism during the final stage, was efficiently oxidized inside the ponds. In such a way only inorganic N and P were observed outside the ponds matching the internal variability. The management of these ponds at this final stage does not induce a negative environmental impact on sorrounding waters, and assures an attractive shrimp harvesting.