Metal contents in tench otoliths: Relationsihips to the aquatic environment

A monitoring of the quality of waters was attempted determining metal accum ulation in target organs as otoliths of freshwater fish. Tenchs of age rang ing between 2 and 10 years were sampled in three different canals receiving wastewater from industrial, agricultural and urban activities. Metal conte nts were determined in both lapilli and asterisci otoliths, using inductive ly coupled plasma-atomic emission spectroscopy (ICP-AES). Analytical data a re reported for minor metals and for some trace metals. Al, Fe and Zn have contents depending on the environment where the fish has lived, while Na, K , Ca and Sr contents are insensitive to the different aquatic habitat. Cons idering the two types of otolith separately, lapilli display a different af finity for trace metals (Al, Fe and Zn), while in asterisci this affinity i s matched only for zinc. The high affinity of zinc for both types of otolit hs suggests using this metal for discriminating the fresh waters by checkin g its accumulation in otoliths, as well as correlating this accumulation wi th age of the fish: a negative power curve equation is proposed. Since high est concentrations are found in individuals of 2-3 yr., it is advisable to use this fish for such environmental studies.