Abstract
In Egypt, both marine and fresh water fish are of considerable importance as a source of meat. El Elaimy et al. (1990) studied the effect of insecticides on the enzymes acetylcholinesterase, adenosine triphosphate carboxylestrase, glutamate pyruvate transaminase and glutamate oxalate transaminase in Nile water fish Tilapia nilotica, T. zilla, Clarais lazera and Chrichrysis auratis. Clarias lazera is one of the most important freshwater fish in Egypt and Africa, well marketable, becoming important in aquaculture. Total production in 1996 from the river Nile only contributes about 17.5% of the total Nile catch in Egypt (Gafrd, 1997). In this study, the relation between the detoxifying enzymes and Nile fish Clarias lazera to resist the insecticide (dimethoate) was examined.