Fishery management options for the critically endangered spotback skate, Atlantoraja castelnaui: the only privileged ones should be the juveniles

Abstract

The spotback skate (Atlantoraja castelnaui) is a large species (≈1400 mm total length)subjected to intense fshing pressure in a multispecies fshery of Uruguay and northern Argentina(34º–41ºS). Despite this, species-specifc landing reports and stock assessments are lacking. Demographic analyses may ofer a comprehensive characterization of the population to examine potential responses to management actions. Here, we used a static age-structured Leslie matrix model to perform demographic analyses on A. castelnaui, with parameter uncertainty incorporated through Monte Carlo simulations. Without exploitation, the fnite rate of population growth (λ) was 1.065 years-1, the net reproductive rate (R0) was 18.032 and generation time (G) was 23.833 years. Elasticity analyses indicated that juvenile survival had greater efects on population growth rates than adult survival or fecundity. Using this model, we explored two management options: (1) fshing mortality applied to all age classes (current situation), and (2) fshing restricted to adults, excluding juveniles. Results indicate that sustainable fshing levels are reached when fshing mortality begins to be applied after sexual maturity. Urgent species-specifc management measures for A. castelanui are needed, where a reduction in juvenile fshing mortality is the most likely measure to efectively mitigate population depletion.