
Numerous numbers of aquatic organisms are living in the aquatic medium which can majorly benefit to the man. However, due to the continuous rise in the development of industries, many of these aquatic flora and fauna are killed because of toxic metals. Heavy metals from natural and anthropogenic sources are continually released into aquatic ecosystem. The toxicity of heavy metal causes long persistence, bio accumulative and non-biodegradable in the food chain. Chromium is known to be a very toxic pollutant introduced into natural waters from a variety of sources including industrial wastes. The heavy metal, chromium can be toxic at even very low concentration when ingested over a long period of time. The aim of the present study is to assess the protein and amino acid content in brain and muscle of the fish Oreochromis mossambicus was exposed to sublethal concentrations of chromium 1/10th (high), 1/15th (medium) and 1/20th (low) of the 96 hour LC50 values for the period of 10, 20 and 30 days. The fish exposed to chromium showed a decrease the level of protein and increase the level of amino acid for 10, 20 and 30 days in brain and muscle. However, no information is on record concerning the three different sublethal concentrations of chromium on the protein and amino acid contents of freshwater fish Oreochromis mossambicus. The objective of the present work was to observe the effect of chromium on protein and amino acid contents in brain and muscle of freshwater fish, Oreochromis mossambicus.