This study presents the parasitic relationship between the leech, Caspiobdella fadejewi, and the juvenile Atlantic sturgeon, Acipenser oxyrinchus. The aim was to determine leech invasion intensity and extensity and describe parasite feeding location preferences on the ventral side of the snout and gill cavities. The prevalence of C. fadejewi occurrence was 37.3%, at an intensity of one to eight leeches. It was confirmed that the intensity of leech occurrence was positively correlated with sturgeon total length (r=0.545, P<0.05, N=15). The host-searching mechanism is most probably based on positive phototaxis. This is the first record of C. fadajewi from A. oxyrinchus. The leech was first observed during routine examinations of sturgeon collected in June 2008. The leeches were usually attached to the inside lower portion of opercula near the isthmus.
