Taxonomic Revision of the Genus Croaker Johnius (Perciformes: Sciaenidae) in Taiwanese Waters

Abstract

Given the identification of the new species Johnius taiwanesis, the Johnius 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 Johnius 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 Johnius forming a monophyletic group. The Johnius species in Taiwan are mainly distributed in a latitude ranging from Xingda (22.4° N) to Hsinchu (24.8° N) with J. taiwanensis, J. distinctus, and J. belangerii representing the most abundant species caught throughout the year. Johnius amblycephalus and J. borneensis were only caught in the summer, while J. trewavasae was rarely caught. In conclusion, we provide a dichotomous key for the genus Johnius in Taiwan waters.