Description of Gerres chrysops sp. nov. from Thailand and redescription ofGerres setifer (Hamilton, 1822) and G-decacanthus (Bleeker, 1865) (Perciformes : Gerreidae)

Gerres chrysops, a new gerreid species from the Gulf of Thailand, is descri bed on the basis of 29 specimens, 58-83 mm in standard length (SL). A small -sized species (less than 100 mm SL), it is characterized by a silvery-gold sheen on the head and trunk, vivid yellow or yellowish-hyaline fins in lif e, two supraneural bones (formula 0/0/2/) and dorsal fin rays usually IX, 1 0. The new species is similar to G. decacanthus (Bleeker, 1865) and G. seti fer (Hamilton, 1822), which are redescribed, being similarly small valid ge rreid species characterized by two supraneural bones. Together, the three s pecies comprise "the Gerres setifer complex." Gerres chrysops differs from both G. decacanthus and G. setifer in life and fresh colors, the body being silvery-gold with vivid yellow or yellowish dorsal, caudal, anal and pelvi c fins, and yellowish-hyaline pectoral fins (vs. silver body with hyaline f ins in the latter two species). Gerres setifer differs from G. chrysops and G. decacanthus in having the last dorsal fin spine longer than the penulti mate spine (vs. almost same length or shorter), usually ten dorsal fin spin es and nine soft dorsal rays (vs. usually IX, 10), and 8 or 9 lower series gill rakers (vs. usually 7). Gerres decacanthus differs from G. chrysops an d G. setifer in having a shorter head, lesser body depth at the first anal fin spine base, lesser body width at the pectoral fin base, and shorter sec ond dorsal and third anal fin spines. The new species is currently known on ly from Angsilla, near Bangsaen, and around Si Chang Island, northeastern G ulf of Thailand. Gerres decacanthus inhabits southern Chinese waters and G. setifer is currently known from the Bay of Bengal to the Andaman Sea.