Lepomis gibbosus is a fish that lives in calm, shallow warm waters, among the moderately abundant vegetation of low or stagnant streams. It is a source of animal protein for humans. However, if it is contaminated with metals, it can be a health hazard. In the present work, we have estimated the degree of concentration of seven metallic elements in the water and in the sediment of the biotope of life, and the liver and gonads of three sizes of Lepomis gibbosus individuals. The studied hydrosystem was the Fouarate Lake which is located near the town of Kenitra and from which it receives liquid and solid waste. The results showed that the sediment was contaminated by the majority of the metallic elements studied. Water is also contaminated but to a lesser extent than sediment. The concentration of these metals varies depending on the organ and the size of the fish. The results also showed that for the liver and gonads were highly contaminated by these metals but, with the exception of chromium whose amount did not exceed the detectable threshold, the degree of this contamination varies according to the organ and depending on the age, otherwise the size of the fish. This contamination could stress the function of detoxification of the body ensured largely by the liver and the reproductive function provided by the gonads. Similarly, Also, Lepomis gibbosus, from the studied lake, can be dangerous for the consumer.