Cl50 de sulfato de cobre pentahidratado en mulinia sp. y su efecto en la supervivencia de postlarvas de litopenaeus vannamei

Abstract

Ecuadorian shrimp production is not exempt from problems such as the proliferation of organisms considered harmful fauna. These include bivalve molluscs such as mussels and clams, which can cause damage to the crop due to competition in space, oxygen, alkalinity and total hardness, and food. These molluscs enter and proliferate in the ponds once they have found the right conditions to complete their life cycle, so it is important act in the best way to control them. In the case of shrimp farms in the province of El Oro, since 2013 has been reported the presence of the clam Mulinia sp., which is very difficult to eradicate. CuSO4.5H2O is for controlling; however, the lack of information about the lethal concentration for this chemical in this species is one of the principal problems. For this reason, we believed necessary to carry out a Median Lethal Concentration (LC50) of CuSO4.5H2O in Mulinia sp., which one providing information at the shrimp producers affected the concentration of this chemical for total elimination and without negatively influence the survival of shrimp Litopenaeus vannamei in the ponds. Two experiments were developed. The first, an acute toxicity bioassay of static type without renewal, for determining the LC50 values of CuSO4.5H2O in Mulinia sp. at 24, 48 and 72 hours. Sixty clams (average shell length of 8.81 ± 1.02 mm) were divided into 12 aquariums. Four concentrations, 0, 0,50, 0,80 and 1,00 mg/l of CuSO4.5H2O (0, 0,32, 0,51 and 0,64 mg/l as CuSO4 or 0, 0,13, 0,20 and 0,25 mg/l as Cu) were tested. Each concentration had three replicates. The number of dead bivalves was counted at 24, 48 and 72 hours. The Finney Probit Analysis was used to process the results, transforming the concentrations of CuSO4.5H2O to its equivalent as CuSO4. The LC50 values of CuSO4.5H2O at 24 and 48 hours were 0.39 mg/l (0.25 mg/l CuSO4 or 0.10 mg/l Cu) and 0.37 mg/l (0.24 mg/l CuSO4 or 0.09 mg/l Cu), respectively. After 72 hours of exposure, the concentrations of 0.8 and 1.0 mg/l caused 100% mortality, so that LC50 could not be determined at this time. The second experiment, also static and without renewal, was performed for evaluating the concentrations and times previously tested on the survival of L. vannamei postlarvae with an average length of 19.0 ± 1.7 mm. Mortality was not observed in all the concentrations evaluated during the first 24 hours, but not at 48 hours, in which 1.0 mg/l produced 3% mortality. Finally, based on these results, it could be concluded that 0.8 mg/l CuSO4.5H2O can be used for 72 hours if it is desired to completely eliminate the bivalves of the species Mulinia sp. without affecting the survival of L. vannamei postlarvae. However, it is important to know that some water quality parameters affect the toxicity of CuSO4. In these experiments, the total alkalinity and salinity of the water were 135 mg/l CaCO3 and 35 PSU, respectively. It is therefore necessary to carry out further studies in order to quantify the influence of these variables on the effect of this chemical on the elimination of Mulinia sp.