Low salinity decreases the tolerance to two pesticides, beta-cypermethrin and acephate, of white-leg shrimp, litopenaeus vannamei

Acute toxic effects of two commonly used pesticides, beta-cypermethrin and Acephate, to the white-leg shrimp, Litopenaeus vannamei, were tested at ambient salinity 5.0% and 20.0%, by using a static renewal method. The results showed that the mean LC₅₀ values of beta-cypermethrin at 24, 48, 72 and 96 h were 0.437, 0.317, 0.203, and 0.170 μg/L to the white shrimp at 5.0%, and were 0.767, 0.440, 0.383, and 0.383 μg/L at 20.0%. The mean LC₅₀ values of Acephate at 24, 48, 72, and 96 h were 51.250, 38.007, 27.783, 18.247 mg/L at 5.0%, and were 59.853, 43.490, 34.220, 27.337 mg/L at 20.0%. L. vannamei is more sensitive to ambient beta-cypermethrin and Acephate toxicity at salinity 5.0% than at salinity 20.0%. Beta-cypermethrin is highly toxic to L. vannamei at either salinity, while acephate has low toxicity to L. vannamei.