Spawning frequency and batch fecundity of Brazilian menhaden, Brevoortia aurea, in the Rio de la Plata estuary off Argentina and Uruguay

The reproductive biology of Brazilian menhaden, Brevoortia aurea, inhabiting the estuarine waters of the Rio de la Plata (Argentina-Uruguay), was studied by using histological analysis of the ovaries. The samples were collected during the peak of the spawning period of this species (November) during 1994, 1995, and 1997. Brevoortia aurea is a multiple spawner with indeterminate annual fecundity. Spawning frequency, determined from the percentage of females with postovulatory follicles, was about 12% during November 1995. At this frequency, each female on average spawned a new batch of eggs about every 8 days. Batch fecundity, estimated from counts of hydrated oocytes, was fitted to a power function of length and a linear function of ovary-free female weight. Batch fecundity estimates ranged from 20,000 (27 cm fork length) to 130,000 (34 cm fork length) hydrated oocytes. Annual differences in the size-fecundity relationship were observed. Relative fecundity estimates obtained from the different years sampled ranged from 60 to 212 hydrated oocytes/g of female (ovary-free weight).