Hematological Changes in Fingerling Channel Catfish Exposed to Malachite Green

Fingerling channel catfish (Ictalurus punctatus) were exposed to 0.1 mg/l malachite green in 40-liter aquariums (fasted fish) and 500-liter troughs (fed fish). In both tests, neutrophilia at 1 and 3 days after treatment was the most drastic hematological change found. Other significant changes (P < 0.05) in the test with fed fish were increases in erythrocyte counts, hemoglobin concentrations, and hemoblast percentages 3 days after treatment; erythrocytosis after 7 days; hematocrit increase after 14 days; and leukopenia after 21 days. No significant differences were found 28 days after exposure.