Fish infection or vaccination induces the production of antigen - specific antibodies by B lymphocyte s. These B cells are recruited based on the specificity of their surface Ab, among the vast diversity of receptors produced through the random and imprecise genomic rearrangement of V, D and J genes during lymphocyte differentiation . In fish , t he monitoring o f B cell response to infections or vaccines has been mainly performed by serological and molecular techniques that provide a limited insight into the complexity of humoral adaptive immune response. We have developed a deep sequencing based approach to comp are the clonal structure of the rainbow trout B cell primary and secondary response against the fish rhabdovirus VHSV . In this approach , u nique barcode labels are incorporated on each starting cDNA molecule before amplification , allowing the correction of PCR/sequencing errors by generating consensus sequence and a safer quantification of sequence relative abundance . We characteriz ed the clonal complexity of the IgM and IgT repertoire during the primary and sec o ndary responses: we identifi ed B cell clonal expansions generated in primary response to VHSV that are still detectable five months after immunization , and analy z ed their frequency after a challenge with the same virus . Our data will be useful to model the development of the Ig landscape , and to understand the mechanisms of B - cell memory after infection by pathogens or vaccin ation in fish.