Variation in the prevalence of the externally visible pathological symptoms affecting Baltic herring

Geographical distribution of Baltic herring (Clupea harengus membras (L., 1761)) affected with externally visible pathological symptoms is demonstrated, based on the observations of 5 028 individuals. The fish were collected in period 25.11-08.12.1994, from 36 sampling hauls performed on a transect from the south-western to the north-eastern Baltic Sea. The results of analyses indicate statistically significant differences in the fraction of herring with externally visible diseases (mean percentage of 3.7%) dependent on the geographical area. A relationship between the prevalence of emaciation (mean prevalence of 3.3%), infection (mean prevalence of 3.7%) in herring with the parasitic larvae of Anisakis simplex (Rudolphi, 1809), and the area of sample collection was shown to exist.