Acute toxicity of 4 aquatic medicines to Lutjanus rivulatus larva

The acute toxicity of formaldehyde, benzalkonium-bromide, povidone-iodine and beta-cypermethrin to Lutjanus rivulatus larva was studied with the method of semi-static water. The result shows that the order of toxicity is beta-cypermethrinpovidone-iodinebenzalkonium bromideformaldehyde. Formaldehyde, benzalkonium bromide and povidone-iodine are low toxicants, and their SC (safe concentration) is 19.880 0mgL-1, 7.571 0 mgL-1and 2.842 9 mgL-1, respectively. Beta-cypermethrin is a highly toxic substance, whose SC is 0.002 8 mgL-1. The 24 h LC50 for formaldehyde, benzalkonium bromide, povidone-iodine and beta-cypermethrin is 81.324 0mgL-1, 40.761 9mgL-1, 15.207 7 mgL-1and 0.015 3 mgL-1, respectively, while 48 h LC50 is 75.958 7mgL-1, 34.741 3mgL-1, 12.989 4 mgL-1and 0.012 9 mgL-1, respectively. It is recommended that beta-cypermethrin not be used in the breeding of L.rivulatus, while benzalkonium-bromide and povidone-iodine be used carefully.