Hybridization between fish species can play a significant role in evolutionary processes and
can influence management and conservation planning, however, this phenomenon has
been widely understudied, especially in marine organisms. The distribution limits of two
sciaenid species (silver kob, Argyrosomus inodorus, and dusky kob, A. japonicus) partly
overlap along the South African coast, where both species have undergone severe depletion
due to overfishing. Following the identification of a number of possible cases of species
misidentification or hybridization (21 out of 422 individuals), nuclear and mitochondrial DNA
data (12 microsatellite loci and 562 bp of the COI gene) were analysed to investigate the
genetic composition of these individuals. Results indicated a field-based species
misidentification rate of approximately 2.8% and a rate of natural hybridization of 0.7%.
Interestingly, all hybrid fish resulted from first-generation (F1) hybridization events, which
occurred exclusively between silver kob females and dusky kob males. Whether
hybridization is the result of natural events (such as secondary contact following a shift in
distribution range), or anthropogenic activities (size-selective pressure due to overfishing),
these findings have important implications for critical recovery and future management of
these species in the wild.