In the first part, this doctoral thesis presents the results of a study of Anisakis spp. nematodes (Dujardin, 1845) in paratenic hosts. Six fish species: anchovy (Engraulis encrasicolus), sardine (Sardina pilchardus), hake (Merluccius merluccius), whiting (Merlangius merlangus), chub mackerel (Scomber japonicus) and tuna (Thunnus thynnus); and one cephalopod (Illex coindetii) were sampled for epizootiologic analysis within the central territory of eastern Adriatic over the course of multiannual fishing and biological research (N = 559) and one-year seasonal sampling (N = 600). In the second part samples for an epidemiological investigation of the coastal population were collected from routine population blood testing from the central Dalmatia. ELISA test results showed an overall seroprevalence of 1,83% IgE titer to Anisakis spp. nematode antigens in the blood sera of healthy blood donors from the Croatian coast. In population subgroups A (islands) and B (City of Split), diverse seroprevalence rates were documented (A = 3.5%; B = 1.5%), whilst the control group C (Dalmatian Zagora) recorded no seropositive examinees. Results have shown the presence (P = 14.2–100%) of genus Anisakis larvae in all sampled fish and one cephalopod species, in total 3,794 larvae. Environmental infection parameters have shown a seasonal character with the highest values during the warm season. In all studied species, a positive correlation was established between the length of the host and abundance of anisakid infection, with the exception of cage-reared tuna, where usually a general decrease in parasite species was noted at the end of the rearing cycle. Molecular characterization of 77 Anisakis spp. nematode larvae, has shown that 74 (96.1%) were identified as Anisakis pegreffii, whilst three larvae (3.9%) belonged to Anisakis simplex. Application of the measures that eliminate biological hazards and better communication with all stakeholders (fishermen, residents and health care workers) could reduce the risk of parasitic infection (anisakidoses) in man.