Effects of Copper Sulfate (CuSO₄) on red tilapia fingerlings (Oreochromis sp.)
Pathogens represent a significant threat to aquaculture, with detrimental effects on the survival of farmed fish. To control these infections, copper sulfate (CuSO₄) has been used as a chemotherapeutic treatment. However, its use presents challenges, as the optimal concentration to minimize adverse health effects in certain species under production conditions remains poorly understood. The aim of this study was to evaluate the effects of acute copper sulfate toxicity on red tilapia (Oreochromis sp.) fry. To this end, 300 fry with an average total length of 2.9 ± 0.31 cm were acclimated for 15 days in a single 250-L tank. Fish were then randomly distributed into fifteen 20-L tanks and subjected to acute exposure for 96 h under five treatments: control, 0.5, 1.0, 2.0, and 4.0 mg/L CuSO₄. Histopathological evaluations were performed on the second gill arch to assess tissue alterations; identified abnormalities included lamellar fusion, congestion, hyperplasia, metaplasia, lamellar atrophy, and mucous cell proliferation. Although the low mortality observed across treatments precluded calculation of the median lethal concentration (LC50), increasing CuSO₄ concentration was associated with a progressive increase in both histological lesions and cumulative mortality, which reached 18 % in the highest exposure group. These findings demonstrate that copper sulfate can induce histopathological alterations in the gills and compromise survival at higher concentrations, underscoring the importance of understanding and mitigating the adverse effects of chemotherapeutic treatments in aquaculture, particularly in species such as red tilapia.