Garfish, (Belone belone) is a migratory pelagic fish that inhabits the waters of coastal Europe, North Africa, the North Sea, the Mediterranean Sea coasts of France, Spain, Portugal, and Morocco, and the North Atlantic. In the Baltic Sea, garfish are staying for several months during spring in the coastal waters of the Bay of Pomerania and the Puck Bay. Large shoals of garfish migrate to the shallow coastal waters of the southern Baltic in late May and early June to spawn. Garfish spawn in shallows with submerged vegetation to which the spawned eggs attach. After spawning and regaining their strength, the garfish shoals migrate to the north Baltic Sea. Garfish is reported very rarely in the eastern parts of the Baltic Sea, and in the region of Finland [8]. Garfish shoal close to the water surface, when escaping they breach the water surface. Garfish is a large, predatory marine fish and feed on crustaceans, molluscs, and small fishes (herring, stickleback, sprat), which they prey upon close to the water surface.

Garfish has a distinguishing feature; its skeleton, scales, and bones are a distinctly blue-green color. The back of the garfish is either dark blue or dark green, its sides are a very shiny silver, and its abdomen is decidedly white with a golden sheen. There are conflicting theories about the chemical compound responsible for this color. Juttner et al. [14] linked this color with collagen, which is a typical physiological character of the garfish. Collagen-rich tissues (periosteal and spinal processes) of garfish contain biliverdin.

The garfish is also known as green bone and horn fish. Specimens with body lengths up to 70 cm are most common, and its maximum length is 100 cm. The largest recorded garfish caught in the southern Baltic Sea measured 89 cm.

Little information about garfish has been disseminated mainly because of its low abundance and its brief occurrence in various water bodies. This fish is not fatty and has few bones. The organoleptic qualities of garfish are similar to those of eel. Few data are available on its nutritional values or the concentrations of contaminants in its muscles. Data available in the literature from analyses of the periosteal and spinal processes of garfish bones indicated that iron concentrations were from two to three times higher in comparison to those in the tissues and bones of other fishes. Staszowska et al. [31] and Turkme et al. [33] studied the macro- and microelements of muscle tissues and confirmed higher concentrations of copper, zinc, and iron in comparison to other Baltic Sea fishes. However, these researchers limited their assessment of toxic compound contamination to that of cadmium and lead, which were detected at very low concentrations in garfish muscle tissues. Data is lacking on mercury compounds, particularly dangerous the toxic organic form of methylmercury, that are typically detected in fishes.

The aim of the present study was to determine the concentrations of total mercury and methylmercury in the muscle tissue of garfish and their correlations with specimen length, weight, age, and sex and also to estimate the potential health risks associated with garfish consumption. Health risks were assessed with toxicity markers including the estimated daily intake (EDI), tolerable weekly intake (TWI), and target hazard quotient (THQ).