ملخص
Anisakis simplex is an nematode, concerned as an internal parasite that affects many species of fishes., such as Atlantic horse mackerel Trachurus trachurus. 75 Atlantic horse mackerel collected during February and March 2018 in Tripoli coast. The results of this study shows that the third stage larvae Anisakis simplex infect the internal cavity of the T. trachurus. At the coast of Tripoli-Libya. The parasite was identified by studying its morphological characters whereby the incidents rate has reached 37.33% and the highest rates were at the range of total length of 20-22cm, and the lowest rates were at the range of total length of 28-30cm; no cases were recorded at range of the total length of 14-18cm.