Life history of a simultaneously hermaphroditic fish, Diplectrum formosum.

Sand perch Diplectrum formosum were collected in the Atlantic Ocean waters off the south-eastern U.S. for life history analyses between April 2001 and July 2004 and ranged in size from 63 to 236 mm standard length (L(S)) and 0-8 years of age. Diplectrum formosum are simultaneous hermaphrodites that reach 50% sexual maturity at 12.2 months and 122.8 mm L(S) for testicular tissue and 13.6 months and 129.3 mm L(S) for ovarian tissue. The gonad contains ovarian and testicular tissue separated by a thin basement membrane, with no means of internal self-fertilization. Spawning females were found between March and January with a peak of spawning activity in May and a realized spawning periodicity of 2 days, equivalent to a maximum of 168 spawning events per year. Fish with testicular tissue in spawning condition were obtained throughout the year in every month sampled with a maximum frequency between June and September. There were also trends indicating that testicular tissue was more likely to be in spawning condition in the presence of hydrated oocytes within the accessory structure. This may indicate the use of the accessory structure as a storage site for hydrated oocytes until a mate can be located.