abstract:Reproductive biology of the big eye, Priacanthus macracanthus, is described based on 601 specimens caught by otter trawl in north-eastern Taiwan waters and landed at Tahsi fishing port from December 1997 to November 1998. Four methods, macroscopic appearance of ovary, gonadosomatic index, oocyte diameter frequency distribution, and histological examination suggested that the spawning season of the big eye in north-eastern Taiwan waters is from April to July and peaks in May and June. Five stages of oocyte development were determined based on histological examination and ovarian development can be divided as undeveloped, developing, matured, and spent stages. Mean fecundity (± SD) was estimated to be 131 112 ± 33 379. Size at first maturity estimated from the Logistic model was 18.9 cm FL corresponding to a 3-year-old specimen.