Hermaphroditism found in adult hatchery-reared greater amberjack Seriola dumerili

The greater amberjack Seriola dumerili is economically important in both capture fisheries and aquaculture. It is a gonochoristic species with no noticeable sexual dimorphism, usually reaching maturity at 3–4 years. Spawning occurs in the Pacific from May to June but varies between regions. During a study on the maturity of greater amberjack, abnormal hermaphrodites (AH) with ovotestes were found. Of the 51 fish examined from June 2017 to April 2018, 2 individuals (3.9%) were classified as AH, with one each identified in February and April 2018. These AHs were larger than the gonochoristic (GC) individuals of the same age. In February, both AH and GCs had sperm-filled seminal lobules and ovaries at the primary yolk stage. By April, atresias were seen in both the AHs and GCs. While oocyte diameter increased in both AHs and GCs between February and April, the gonadosomatic index was lower in AHs. Plasma estradiol-17β and 11-ketotestosterone levels of AHs were similar to those of male GCs. These results suggest that AHs have accelerated growth with potential maturation as functional males. This is the first report on hermaphroditism in the Seriola genus.