TRACE METALS DEPOSITION IN OTOLITES OF PSECTROGASTER AMAZONICA AS ENVIRONMENTAL INDICATORS IN THE MIDDLE TOCANTINS RIVER

The growing expansion of aquaculture and the increasing pollution of water bodies have raised concerns about the accumulation of trace metals in aquatic organisms, particularly fish. In this context, otoliths, structures located in the inner ear of fish, stand out as important tools for environmental monitoring, being used to assess the presence of pollutants and identify species based on the morphology of these structures. This study investigated the morphometry of otoliths and the deposition of trace metals (Calcium, Aluminum, Vanadium, Potassium, Copper, Iron, Magnesium, Indium, Gold, Tin, Mercury, and Manganese) in Psectrogaster amazonica from the middle Tocantins River, Maranhão, Brazil. Otoliths from 37 specimens were analyzed using inductively coupled plasma optical emission spectrometry (SHIMADZU, ICPE-9000, Kyoto, Japan) to quantify trace metals. Morphometric data were used to calculate shape indices such as roundness, circularity, rectangularity, ellipticity, and form factor, correlating these indices with pollutant presence. Among the elements analyzed, Aluminum (0.823 mg/L), Vanadium (0.382 mg/L), and Copper (0.035 mg/L) showed average concentrations exceeding certain national and international standards. The aluminum results are particularly concerning, as previous studies along the banks of the Tocantins River have reported elevated levels of this metal in water and sediments. These findings suggest that P. amazonica can serve as an environmental biomarker, contributing to understanding pollution levels in aquatic environments and highlighting the importance of otoliths in ecological assessments.