Vulnerability to exploitation of the yellownose skate (Dipturus chilensis) off southern Chile

The yellownose skate (Dipturus chilensis) is one of the most important component of the commercial elasmobranch fishery off Chile with an extensive distribution range from 36°44′ S − 55°13′ S. Nevertheless, fishery management for this species does not extend beyond the central zone off Chile (36°44′ − 41°28′ S), leaving the southern zone (41°28′ S − 55°13′ S) without a proper fishing effort regulation. As a result, fishing pressure has increased dramatically in the southern zone, with unknown potential consequences for this elasmobranch population. In the absence of rigorous fishery-biological data, we used a matrix population model to assess yellownose skate demographic traits under different fishing mortality levels. A Leslie matrix model was implemented, where changes in age classes are defined in terms of of life history parameters. Uncertainty was incorporated by applying a Monte Carlo method to survival, age at maturity, and fecundity. Three scenarios were evaluated based on different assumptions about survival, fishing mortality rates, and age at 50% of vulnerability. These scenarios showed a slow growth rate for population abundance (3-15% per year) with no fishing exploitation. The population reaches equilibrium at low mortality levels (0.31 yr−1), which is consistent with estimates reported for other rajidae skates. The elasticity analysis indicates that juvenile survival contributes the most to variations in the population growth rate. The sustainable mortality rate has a positive, non-linear relationship with age at 50% of vulnerability. Projections using different selectivity patterns showed that the population abundance is stable only when age-dependent fishing mortality removes individuals of older ages. We concluded that yellownose skate is extremely vulnerable to fishing exploitation and it is remarkably sensitive to juvenile and early life stages survival, implying that management actions are needed to ensure a sustainable exploitation.