Reproductive Biology and Annual Variation of Reproductive Variables of Black Drum in the Northern Gulf of Mexico

Black drums Pogonias cromis were sampled from commercial and recreational catches in the northern Gulf of Mexico from July 1987 to September 1990, Seasonal onset of spawning, evidenced by the presence of postovulatory follicles in ovarian tissue sections and by elevated gonadosomatic indices, occurred in January of each year (one female with hydrated oocytes was sampled in December 1988). Atretic oocytes observed in mid to late April indicated imminent cessation of spawning. Two of 115 females less than age 5 had achieved sexual maturity; all females age 5 and older were mature. Fifty percent maturity of females was attained at 640–649 mm fork length and all females larger than 690 mm were mature. Male black drums entered the breeding population at a younger age (>50% maturity at age 4) and a smaller size (50% maturity at 610–620 mm). Multiple oocyte stages observed throughout the annual spawning seasons verified groupsynchronous oocyte development and multiple batch spawning. Estimated batch fecundities of 41 females with hydrated oocytes ranged from 0.51 million to 2.42 million ova. Mean batch fecundities were 1.22 million ova for the 1988 spawning season, 1.65 million ova for 1989, and 1.21 million ova for 1990, Batch fecundity was positively correlated with total weight, fork length, eviscerated body weight, and age, Spawning frequencies estimated from the proportion of mature females with postovulatory follicles were one spawning event per 3.0 d in 1988, one per 4.2 d in 1989, and one per 3.9 d in 1990. A protracted spawning season, generous batch fecundities, and frequent spawning provide black drums with annual fecundities of 13 million to 67 million ova.