The aim of this study was to show the influence of environmental conditions on the ionic composition of fish bones. The analysis concerned the ionic structural composition of the operculum in fish species with different abiotic habitat preferences. Three species of fish were examined: cod, Gadus morhua L., 1758; sea trout, Salmo trutta morpha trutta L., 1758 and perch, Perca fluviatilis L., 1758. Results from hydrochemical research on salinity in the Pomeranian Bay (Southern Baltic) were also utilized. Using the determined ratios (Ca:Mg, Na:Mg, Sr:Ca and Na:Ca in the operculum and Ca:Mg, Na:Mg and Na:Ca in the waters of the Pomeranian Bay), typical correlations were determined for the analyzed habitat. Macrocation structure in the operculum bones for each species were found to be as follows: - cod: Ca – 32.3%, Mg – 29.8%, Na – 1.4%, K – 0.8%, Sr – 2.1%; - sea trout: Ca – 22.8%, Mg – 13.5%, Na – 0.8%, K – 0.2%, Sr – 1.7%; - perch, Ca – 37.9%, Mg – 15.1%, Na – 2.4%, K – 0.7%, Sr – 1.6%.