We analyzed biological data of splendid alfonsino Beryx splendens in the Emperor seamounts shared by NPFC Members to define the reproductive season and maturity stages and to estimate size at sexual maturity (FL₅₀). Monthly changes in gonadosomatic index and maturity stages based on macroscopic and microscopic analyses suggests that reproduction occurs between March and December. The FL₅₀ values estimated by a logistic regression model ranged between 257 and 365 mm. This differences in estimates may be related to differences in fish size used in the analysis, sampling location, and year. Therefore, further analysis considering temporal and spatial variability is needed to estimate more reliable FL₅₀ for stock assessment of Beryx splendens in the Emperor seamounts area.