Effect of different concentrations of deltamethrin on the growth of white leg shrimp (Litopenaeus vannamei) exposure to different salinities

Abstract

Deltamethrin is a pyrethroid pesticide used extensively to eliminate wild crustaceans in shrimp ponds, treat the water quality and reduce diseases.This study aimed to investigate the combined effect of salinity and concentration of deltamethrin on the growth of white leg shrimp (Litopenaeus vannamei) in laboratory condition. The experiment was set up indoor and randomly designed with 4 different salinities such as 10, 15, 20 and 25 ppt in 2 concentrations of deltamethrin including: 5% LC50 and 10% LC50. The control treatment was the salinity of 15 ppt with no deltamethrin supplement. After experiment, the result showed that shrimp displayed some external clinical signs such as soft shell, black spots in the shell, rot in the tail and appendages. Some shrimp showed gill cover flear off. First clinical signs were recorded within 24h in shrimp exposed to 5% LC50 and 10% LC50 deltamethrin concentrations at 10 ppt, 15 ppt as well as 20 ppt salinities. No mortality was bserved in the controlled treatment and the treatment 20 ppt 10% LC50. The highly significant mortality occurred in the treatment 15 ppt 10% LC50 at 44.4%. The higher concentration of deltamethrin can cause high mortality in the same salinity level. In addition, in the same concentration, the lower salinity the higher mortality recorded. The results indicated that L. vannamei at lower salinity is more sensitive to the toxicity of deltamethrin than in higher salinity.