Reproductive Biology of Johnius taiwanensis (Perciformes: Sciaenidae) in Fujian Waters, Southern China.

Johnius taiwanensis is a newly described species from the Family Sciaenidae (Perciformes). The species is commonly found in shallow coastal waters along both sides of the Taiwan Strait, on the west sides of Zhejiang, Fujian, Guangdong and Hong Kong and east side of Taiwan, and has been misidentified for decades. We studied the reproductive biology of J. taiwanensis from Fujian coastal waters, southern China, using gonadosomatic index (GSI) and gonad histology analyses. Monthly sampling from July 2016 to October 2017 was conducted and a total of 638 specimens were collected, ranging from 7.3 to 19.0 cm standard length (SL). Gonad histology suggested that the spawning activity of J. taiwanensis females and males lasted from April to October, and the peak spawning months for females was July to September. Mature females and males were 12.5 and 11.8 cm SL, respectively, while the estimated sizes at 50% maturity were 12.0 cm and 10.9 cm SL, respectively. Vitellogenic stage oocytes (O3) and post-ovulatory follicles (POF) or hydrated oocytes (HO) were observed, and POF and O3 in ovaries indicated that J. taiwanensis spawns multiple times each spawning season. HO or both HO and POF were observed in ovaries collected from one same location in May 2017 and August 2016.