Spawning and fecundity of striped weakfish, Cynoscion guatucupa, in the Río de la Plata estuary and adjacent marine waters, Argentina–Uruguay

The reproductive biology of the striped weakfish, Cynoscion guatucupa, inhabiting the estuarine waters of the Río de la Plata and adjacent marine zone (Argentina–Uruguay), was studied using macroscopic and histological analysis of the gonads. The samples were collected from three research cruises carried out during the spawning period in March 2000, 2001 and December 2003. Length at first maturity estimated for both sexes was 27.20 cm total length (TL) in March 2000 and 30.66 cm TL in December 2003. Batch fecundity ranged from 14,500 to 208,000 hydrated oocytes and was positively correlated with total length and ovary-free female weight. Relative fecundity estimated for the 3 years sampled ranged between 37 and 276 hydrated oocytes/g. During December 2003, fecundity values were significantly lower than those obtained in March 2000 and 2001. However, in December the oocyte dry weight was greater than in March, when the spawning activity of striped weakfish decreases.