The endoparasites of whiting, Merlangius merlangus euxinus from the Turkish Coast of the Black Sea were investigated during the years 1990-1993. Only the endoparasite, Hysterothylacium aduncum (Nematoda: Anisakidae) was recorded in all visceral organs examined. The prevalence and intensity of H. aduncum were significantly higher in the warm season (July-August) than in the colder period (January-February) (P<0.01). Infection increased significantly with age and length of the fish (P<0.01). The relationship between fecundity and length for infected and uninfected fish was calculated as log F=2.492 log L+1.531 and log F=2.611 log L+1.408, respectively. No significant difference between infected and uninfected fish was seen in either the fecundity-length data or the condition factor (P>0.01). (C) 1999 Elsevier Science B.V. All rights reserved.