Studies on the biology of non-commercial species, based on the example of the fourbeard rockling Enchelyopus cimbrius (L., 1766) (Gadiformes: Lotidae) in the southern Baltic

The paper includes a detailed analysis of selected elements of the biology of the forebeard rockling. The study was conducted in the southern Baltic Sea. The sex structure, fertility, stomach contents, age, and growth of the species were analysed. As a result of the study, double predominance in numbers of males over females and high diversity in terms of development and size of oocytes were determined, suggesting partial spawning. A strong correlation was recorded between fertility and body mass and length. The analysis of the content of the fish stomachs revealed dominance of Polychaeta, Crustacea, and fish. Analyses of age and growth were also conducted, based on the otoliths. Individuals of 4 to 13 years of age were found. In the samples analysed, males were older than females. Additionally, differences in growth between the samples analysed were determined, along with similarities in growth between fish collected from the southern Baltic and the Atlantic forebeard rockling.