Reproductive biology of alfonsino Beryx splendens

The main aim of this work is to provide a detailed analysis of the reproductive cycle of Beryx splendens in the Juan Fernández Archipelago. The gonadosomatic index (I(G)) and maturity ogives in both sexes were estimated using an extensive database collected by onboard scientific observers between January 2006 and October 2009. A histological analysis of maturation was also completed for females collected between May and December 2001. Variations in both I(G) and proportion of mature individuals were observed in fish with a fork length (L(F)) >37 cm for females and >33 cm for males. The main reproductive season was in the austral winter and spring (June to November). Fork length at 50% maturity (L(50)) was estimated as 39·67 cm for females (95% c.i. =39·34, 40·02 cm) and 36·88 cm for males (95% c.i. =36·45, 37·36 cm) using macroscopic analysis of gonads. Estimates for females using histological data varied slightly with an estimated L(50) of 43·67 cm (95% c.i. =42·82, 44·91 cm). Changes in I(G) and maturity were modelled as a function of month and L(F) within a generalized additive model framework. A high porportion of immature individuals were found throughout the year. The results of this study are compared with reproductive traits reported for B. splendens in other areas of its distribution and are discussed with reference to exploitation, vulnerability and conservation of the B. splendens stock in Juan Fernández Archipelago.