Background. The king angelfish, Holacanthus passer Valenciennes, 1846, is one of the principal species captured in the Gulf of California, Mexico, for the purpose of the aquarium trade. Although the species has been exploited for more than 40 years, studies have not yet been undertaken to understand the population parameters required for adequate management of the fishery. The objective of this work was to describe for the first time the growth and mortality of this species. The information provided in this study contributes to the generation of knowledge necessary to establish sustainable management practices. Materials and methods. The growth curve of the species was determined by applying a modal progression analysis of the sample length frequency distribution to determine the number of cohorts present through the multinomial statistic based on a probability function. Once the cohorts were identified, the von Bertalanffy growth model was adjusted using a maximum likelihood function. To estimate the natural mortality rate and natural mortality-at-age, empirical methods were used. Were also estimated the size and age at first maturity (Lm, tm), the maximum age (tmax), the fishing mortality (F), the total mortality (Z), and the exploitation rate (E). Results. In total, 794 king angelfish were measured and weighed, including 659 juveniles and 135 adults. The total length of the fish ranged from 3 to 29 cm, and the weight was within 2–797 g. The potential weight–length relation was significant (r2 = 0.94; P > 0.01), showing a negative allometric curve with the parameters: a = 0.108 and b = 2.618. The parameters of the von Bertalanffy growth equation were: L∞ = 37.894 cm, k = 0.127 year–1, t0 = – 0.658 years. The natural mortality rate was estimated to be 0.315 year–1. The following values were estimated for: Lm = 21.835 cm, tm = 6.10 years, tmax = 20.01 years, Z = 1.19 year–1, F = 0.88 year–1, and E = 0.74. Conclusion. Estimates of natural mortality could be linked to management measures such as catch quotas.

von Bertalanffy, natural mortality, fisheries management, weight–length, aquarium fish