An immunoassay may be either quantitative or qualitativeanalytical technique, depending solely on the specificity and affinity of the interaction betweenantigenic epitopeand the paratope of the antibody for generation of a detectable response. The lecture is centered on the several batteries of assays for assessing systemic and adaptive immune mechanisms and thereby assessing fish health. Though the advent of molecular techniques has made disease diagnosis more efficient, few advantages still stand out in favour of immunoassays.