Age, growth and maturity of an endemic valuable resource, the Rio skate (Rioraja agassizii (Chondrichthyes: Rajiformes)), off Uruguay and northern Argentina

Abstract

Context

Rioraja agassizii is a vulnerable species endemic to the Southwest Atlantic. It is caught by trawl fisheries throughout its range.

Aims

To determine the age, estimate growth parameters, and age and size at maturity.

Methods

Ages were determined using vertebrae readings. To fit growth models, a Bayesian framework was employed with the von Bertalanffy, Gompertz and Logistic candidate models. To estimate age and size at maturity, a logistical ogive was fitted to binomial maturity data.

Key results

Maximum ages determined for males and females were 12 and 11 years respectively. The von Bertalanffy model was selected as the best one and there were no differences between sexes (mean parameters: L_∞ = 684.8 mm, k = 0.33 years⁻¹ and L₀ = 105.5 mm). Age and size at maturity were estimated at 3.31 and 4.55 years, and 485.02 and 544.55 mm TL for males and females respectively.

Conclusions

Rioraja agassizii has a moderate growth rate and age at maturity was similar to those of skate species with a similar body size.

Implications

Because skate species have different maximum ages, growth rates and maturity parameters, we strongly recommend urgent species-specific management measures for the pool of skate species exploited in Argentina.