By A.K. Kumaraguru, F.W.H. Beamish
Water Research, Volume 15, Issue 4, 1981, Pages 503-505, ISSN 0043-1354, DOI: 10.1016/0043-1354(81)90061-0.

Lethal toxicity of permethrin varied inversely with water temperature and body weight. The 96 h LC 50 (median lethal concentration) for 1 g trout increased by an order of magnitude from 0.62 to 6.43 [mu]g 1-1 between 5 and 20[degree sign]C. However between 5 and 10[degree sign]C the 96 h LC 50 changed little from 0.6 [mu]g 1-1. Large trout (200 g) were considerably more tolerant to permethrin than small fish. Thus, the 96 h LC 50s for 1 and 200 g trout were 3.17 and 314 [mu]g 1-1 respectively at 15[degree sign]C. The size effect was most pronounced between 1 and 50 g.
It is to be noted that the application of permethrin for insect control coincides with the usual period of emergence of rainbow trout fry subsequent to a spawning period of April to late June.

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