Age, growth, maturity and extinction risk of an exploited and endangered skate, Atlantoraja castelnaui, from off Uruguay and northern Argentina

Abstract

The spotback skate Atlantoraja castelnaui (Arhynchobatidae) is a large and threatened skate species subjected to fishing pressure, endemic to the Southwest Atlantic that occurs from Rio de Janeiro, Brazil, to San Jorge Gulf, Argentina. The age, growth, age at maturity and the maximum intrinsic rate of population increase rmax of A. castelnaui were studied using 152 specimens collected from off Uruguay and north Argentina (35°–42° S), between June 2013 and February 2020. Vertebrae from 143 individuals were used for ageing (females: n = 83, size range 404–1300 mm total length, TL; males: n = 60, size range 400–1270 mm TL). Maximum ages determined for females and males were 30 and 28 years, respectively. To fit growth models, non‐linear and Bayesian estimation approaches were considered. For the first approach, a set of four candidate growth (size‐at‐age) models were fitted: three‐parameter von Bertalanffy, two‐parameter von Bertalanffy with fixed L0, Gompertz and Logistic. In the second approach, von Bertalanffy, Gompertz and Logistic were fitted. For non‐linear estimation, model selection indicated that the entire set of candidate growth models were supported by the data. The von Bertalanffy was selected as the best model for Bayesian estimation. There were no differences in growth between sexes. For the sexes combined, the von Bertalanffy growth model by Bayesian method was considered the most adequate to describe the growth of A. castelnaui (growth mean parameters ± S.D.: L∞ = 1210.29 ± 40.68 mm; k = 0.12 ± 0.01 years−1; L0 = 179.20 ± 11.62 mm). The age at maturity was estimated at 16.21 and 14.04 years for females and males, respectively. The maximum intrinsic rate of population increase rmax was estimated as 0.252 years−1. Life‐history traits and rmax provided in the present study suggest that this species has a relatively low productivity and may be vulnerable to an intense fishing pressure.

Life‐history traits of an exploited skate: The short‐tail yellownose skate Zearaja brevicaudata (Chondrichthyes: Rajiformes)

“…In addition, the parameters estimated from the Zavatteri, 2010). Furthermore, the k parameter estimated for Z. brevicaudata agrees with those of species with low productivity and a similar body size, like Bathyraja griseocauda (k = 0.05 for males and 0.07 for females) (Arkhipkin et al, 2008) and Atlantoraja castelnaui (k = 0.11 for males and 0.12 for females) (Barbini et al, 2021).…”

“…Age at maturity is variable among skate species (Cailliet & Goldman, 2004). The ages at maturity of Z. brevicaudata align with those of skates exhibiting large body size, such as B. griseocauda (Arkhipkin et al, 2008); the longnosed skate Dipturus oxyrinchus L. 1758 (Bellodi et al, 2017), and A. castelnaui (Barbini et al, 2021).…”

“…Therefore, a latitude span of 20° or more, such as the one of Z. brevicaudata , may represent a long enough distance to produce population differentiation. Comparing age and growth parameters of the same species at a regional scale can contribute to population monitoring and identification of potential long‐term effects of fishing pressure (Barbini et al, 2021). Therefore, it is crucial to establish a common criterion for age determination and growth parameter estimation to accurately identify temporal changes in life‐history traits within the same population or between populations.…”

“…In addition, growth correlates with several life‐history traits that influence the response of species to exploitation, like natural mortality rate, lifespan, and reproductive allocation (i.e., amount of energy invested in reproduction) (Cailliet, 2015; Pardo et al, 2013), showing a tendency for slow‐growing species to be large‐bodied, to mature later, and to have lower annual reproductive output (Frisk et al, 2005). Moreover, age and growth studies, as well as estimates of age at maturity, are essential to understand the life history of a species and to establish management and conservation measures (Barbini et al, 2021).…”

“…life history of a species and to establish management and conservation measures (Barbini et al, 2021).…”