Ladik Lake (Samsun, Turkey) is a natural landscape under the threat of pollution because of urban, agricultural and industrial activities. In this study, accumulation of heavy metals (Al, Ba, Cr, Cu, Fe, Mn, Pb and Zn) in the tissues (muscle, liver and gill) of sediment dwelling pike fish and in different substrates of Ladik Lake were investigated. Seasonal haematological, biochemical and histopathological parameters of the carp are also reported. In general, heavy-metal levels in water and sediment samples were found in the highest level in summer and the lowest in autumn. Histopathologic changes in the tissues of the fish (liver and gill) were at the minimum in winter while it was highest in summer. Blood biochemical parameters exhibited higher level in summer in comparison with other seasons. Al, Ba, Cr, Mn and Zn levels in the tissues of the fish were in the order gill>liver>muscle in all seasons. The levels of Cu, Fe and Pb were in the sequence liver>gill>muscle. Cr, Cu, Pb and Zn levels were determined to be in high level in the tissues of the fish with respect to the literature values. The heavy-metal levels in Ladik Lake and the fish health need to be regularly monitored for a sustainable environmental health.