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Summary

An Atlantic cod, Gadus morhua L., with unique golden pigmentation was caught during a commercial trawl on the Svalbard Bank. Stomach content analysis excluded the possibility of golden pigmentation resulting from diet. Skin morphology, mitochondrial and molecular species markers and also the concentration of melatonin (MEL) were examined. Skin samples from five areas below and above the lateral line contained correctly developed melanophores, but their distribution was different from those observed in the skin samples of standard coloured cod. Only the difference between the numbers of melanophores below the lateral line was statistically significant (8 vs 19.8 in standard coloured cod). DNA analyses allowed exclusion of the possibility of interspecies hybridisation with haddock Melanogrammus aeglefinus. MEL concentrations in the skin sample of the golden cod compared to the control sample of standard coloured cod were similar and with no statistically significant differences. Some abnormalities observed in the detailed morphology and melanophore distribution suggest a genetic or hormonal nature in the golden pigmentation of the cod. Some of these, e.g. mutations of TYR (tyrosinase) genes or of the MSH (melanophore-stimulating hormone) level can be tested in further analyses.