Abstract
Abstract Diplodus annularis are common public seafood in Libya. Parasites like crustaceans are dangerous threats to fish species because they can lead to less quality seafood production besides the shortcuts of the fish life cycle that significantly affects marine life's biodiversity. So, it was recommended to follow upthe health status of fish by identifyingand counting different parasites spread in Libyan seawater, especially around Tripoli. This research aims to evaluate the common parasites ofD.annularis. About ~ 3300 g of fish samples (60 individual units) were examined for the presence of helminthesendoparasites, copepods, branchiura, and isopoda. Results evaluated in terms of prevalencepercentage with different ranges of length and weight of fish samplesin addition to maturity. Results prove that branchiura (Argulus purpureus) and isopoda (Ceratothoaoestroides) are the common parasites that lived on D.annulariswith the highest percentage of infestation ~ 10.34 and 4.35 % for (12-14) and (14-16) cm length respectively. The sex of a D.annularisspecies was confirmed by examining the genital papilla located behind the anus and findinga balance between the numbers of malesand females, but male are more infested than female samples. A correlation between length, maturityand infection wastheoretically confirmed by applying a mathematical exponential model tomale and female and hence probability function of maturity and parasitological infectionof D.annulariscan be expected within a particular length range.