Demographic Parameters of Golden Spotted Rock Bass Paralabrax auroguttatus from the Northern Gulf of California

The sex ratios, growth, and mortality of the golden spotted rock bass Paralabrax auroguttatus (Serranidae) were determined for populations from Islas Encantadas and Bahía de los Angeles in the Gulf of California. Specimens ranged from 137 to 479 mm standard length and from 135 to 3,100 g. Sagittal otoliths were used to determine age. A von Bertalanffy model of growth for both populations combined was estimated as Lt = 474.4·(1 − e −0.115( t + 2.093)), where Lt is fish length at age t. This model is comparable to those for other rock basses. The relationship between length and weight (W) followed the power function W = 0.00002·L 3.0797 (r 2 = 0.96) with no difference between males and females. The mortality rate was estimated as 49% per year for fish of age 5 and older. In our Bahía de los Angeles samples, the sex ratio was significantly skewed, with more males than females. The mean size of females was significantly smaller at Bahía de los Angeles than in Islas Encantadas. Examination of the sex ratios for these two populations suggested that this species is gonochoristic.