Synechococcus and Prochlorococcus are the numerically dominant primary producers in the oceans and contribute significantly to global primary production. They are infected, among others, by T7-like cyanophages. Phylogenetic analyses show two discrete T7-like lineages, clade A and B. Phages from clade B encode the psbA photosystem II gene and infect either Synechococcus or Prochlorococcus, whereas phages from clade A lack psbA and primarily infect Synechococcus. Using a novel, quantitative, culture-independent method, polonies, we found that clade B phages were at least an order of magnitude more abundant than clade A phages in the Red Sea along depth profiles collected monthly during 2013. Maximal abundances of up to 1.3*10⁶ phages•ml^-1 were found in summer-autumn when cyanobacterial abundances were also greatest. The abundances of T7-like cyanophages from clade B were strongly correlated with Prochloroccocus during periods of stratification. Furthermore, at least in spring, clade A and Synechococcus abundances were highly correlated. These findings indicate that the clade B T7-like cyanophages that carry the psbA gene and infect either host genus are highly abundant throughout the year in the Red Sea.