Effects of fish size and water temperature on the acute toxicity of boron to Japanese flounder Paralichthys olivaceus and red sea bream Pagrus major

The acute toxicities of boron were examined for Japanese flounder Paralichthys olivaceus and red sea bream Pagrus major in terms of fish size and water temperature. Japanese flounder of 0.1-70.0 g and red sea bream of 0.6-20.3 g were exposed to different concentrations of boron for 96 hat 20 degrees C under semi-static conditions. In both fish species, the median lethal concentration (LC50) for 96 h of boron increased linearly with increasing fish size, ranging from 108 to 252 mg B/L for the flounder, and from 97 to 172 mg B/L for the sea bream. The effect of water temperature on acute toxicity was examined for Japanese flounder of 0.6 and 1.5 g at 10, 15, 20 and 25 degrees C, and for red sea bream of 0.6 and 2.4 g at 12, 15, 20 and 25 degrees C. The toxicity of boron for the flounder increased linearly with increasing water temperature. The 96 h LC50 values ranged from 299 to 108 mg B/L for the 0.6 g flounder and from 350 to 113 mg B/L for the 1.5 g flounder. A similar trend was shown for the 2.4 g red sea bream; however, the relationship for the 0.6 g red sea bream was not significant.