Taxonomic Revision of the Genus Croaker <i>Johnius</i> (Perciformes: Sciaenidae) in Taiwanese Waters

Given the identification of the new species <i>Johnius taiwanesis</i>, the <i>Johnius</i> genus in Taiwanese water is here reviewed through a collection of field samples, museum specimens, and a review of the Taiwanese scientific literature. Seven valid <i>Johnius</i> species were successfully identified and distinguished based on gill raker length, tip of upper jaw to mouth hinge length, tip of lower jaw to mouth hinge length, and length of second spine of anal fin. Our phylogenetic tree based on cytochrome oxidase subunit I (COI) showed the existence of high interspecific genetic diversity within the genus <i>Johnius</i> forming a monophyletic group. The <i>Johnius</i> species in Taiwan are mainly distributed in a latitude ranging from Xingda (22.4° N) to Hsinchu (24.8° N) with <i>J. taiwanensis</i>, <i>J. distinctus</i>, and <i>J. belangerii</i> representing the most abundant species caught throughout the year. <i>Johnius amblycephalus</i> and <i>J. borneensis</i> were only caught in the summer, while <i>J. trewavasae</i> was rarely caught. In conclusion, we provide a dichotomous key for the genus <i>Johnius</i> in Taiwan waters.