In this review, different diagnostic techniques for identifying etiology of fish disease are described. Among microscopic techniques, we find rapid diagnostic tests to observe parasites, gill diseases and bacteria; routine histopathological techniques are also used. In samples having bone tissue, decalcification methods are employed. In recent years, apart from using immunohistochemistry and electron microscopy, morphological techniques allow a deep study of disease pathogenesis. At present, molecular techniques for pathogen identification and atomic-absorption spectrophotometry to measure the concentration and distribution of toxic metals in tissues they also use. In conclusion, different techniques can contribute to the evaluation of disorders and provide tools for a better understanding in fish medicine.Facultad de Ciencias Veterinaria
