Waterborne calcium and nitrite interaction: survival, growth, hematological and metabolic parameters in silver catfish

Abstract

The objective of this study was to determine the effect of different waterborne nitrite (NO₂^-) and calcium (Ca²⁺) levels on growth, biochemical and hematological parameters of silver catfish juvenile (Rhamdia quelen). Fish were submitted to low (0.05 mg L^-1) or high (1.3 mg L^-1) NO₂ and low (7 mg L^-1) or high (14 mg L^-1) Ca²⁺ levels (four replicates) for 60 days. At the end of the experimental period, fish exposed to high NO₂^- showed lower weight gain, biomass and specific growth rate than those maintained at low NO₂, irrespective of Ca²⁺ levels. Fish exposed to high NO₂/low Ca²⁺ presented higher lactate levels in the muscle than control fish, but an increase of waterborne Ca²⁺ levels avoided this increase. Fish kept at high NO₂/high Ca²⁺ showed higher lactate levels in the liver than those exposed to low NO₂/high Ca²⁺. Exposure to high NO₂ or high Ca²⁺ alone reduced hepatic glycogen, protein and glucose levels. Fish kept at high NO₂/high Ca²⁺ presented a decrease in hemoglobin levels compared to those kept at low NO₂/high Ca²⁺. Therefore, the use of 14 mg L^-1 Ca²⁺ in water did not minimize the toxicity of nitrite for Ramdia quelen.