Indication of Density‐Dependent Changes in Growth and Maturity of the Barndoor Skate on Georges Bank

Observer data from the commercial fishery on the Patagonian shelf and slope around the Falkland Islands (home to an assemblage of >16 skate species (Rajiformes), for which commercial catches have been recorded since 1987), as well as survey data from an area closed to skate target fishing after exploitation, were summarized by species to examine changes in the population status of individual skate species. Total skate catch per unit effort increased significantly in the target fishery since 1994, and four species have made up >85% of all skate catch. Bathyraja brachyurops and Zearaja chilensis increased significantly in catch proportions and abundance from 1994 to 2013. Bathyraja albomaculata and Bathyraja griseocauda decreased significantly before rebounding with trends of increasing abundance. Concurrently, B. brachyurops and Z. chilensis showed decreasing trends in size at 50% maturity in areas where skates continue to be targeted commercially. The increasing abundances and concomitant reductions in size at maturity of B. brachyurops and Z. chilensis suggest either plasticity in life-history traits or a density-dependent growth response to fishing pressure. Bathyraja griseocauda decreased in size at 50% maturity in the area that was closed to skate target fishing, where it was initially larger, but only decreased to the same average size as in the commercially targeted areas. Bathyraja albomaculata and Z. chilensis are IUCN-listed as vulnerable and B. griseocauda is listed as endangered, but their abundance trends since 1994 indicate that these populations are not declining in Falkland waters.

Section: Discussionmentioning

confidence: 53%

Interannual variability in the skate assemblage on the South Patagonian shelf and slope

Winter

Pompert

Arkhipkin

et al. 2015

“…Therefore, these differences may be related to different regional scales or may be explained by the fact that there are several years of intense exploitation of this species between these two studies. Empirical evidence of density‐dependent changes has been reported for elasmobranchs species that have suffered harvesting over several years, involving changes in their biological parameters (Carlson & Baremore, 2003; Coutré et al, 2013; Sminkey & Musick, 1995; Sosebee, 2005).…”

Section: Discussionmentioning

confidence: 99%

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

Bianchi,

Roman,

Lucifora

et al. 2024

The short‐tail yellownose skate, Zearaja brevicaudata, occurs off southern Brazil and along the Argentine continental shelf, including waters surrounding the Islas Malvinas and the upper slope, and is very frequently caught by trawl fisheries throughout its range. The age, growth, and maturity of Z. brevicaudata were investigated using 204 individuals collected by commercial fishing vessels from northern Argentina, between March 2016 and September 2019. Age was determined on a sample comprising vertebrae from 151 individuals, 60 males, ranging in size from 391 to 956 mm total length (TL), and 91 females, ranging in size from 324 to 1060 mm TL. Maximum ages determined for males and females were 22 and 29 years, respectively. A Bayesian framework was employed with a set of three candidate models to estimate growth parameters (von Bertalanffy, Gompertz, and Logistic). The von Bertalanffy model had the best fit, and the sexes showed undistinguishable growth parameters. For sexes combined, derived growth mean parameters (± S.D.) were L∞ = 1081 mm ± 64.34 mm, k = 0.09 ± 0.01 years−1, and L0 = 248 mm ± 23.52 mm. The age at maturity was estimated at 13.15 and 14.66 years for males and females, respectively.

“…For example, Bathyraja griseocauda (Norman 1937) in Patagonian waters attain 1570 mm TL and a maximum age of 28 years (Arkhipkin et al ., 2008), Beringraja rhina (Jordan and Gilbert 1880) from the Gulf of Alaska attain 1400 mm TL and a maximum age of 25 years (Gburski et al ., 2007) and Dipturus oxyrinchus (L. 1758) from the Gulf of Gabés in the Mediterranean attain 1500 mm TL and a maximum age of 25 years (Kadri et al ., 2014a). Comparing age and growth parameters of the same species on a regional scale may help to monitor populations and identify potential long‐term effects of fishing pressure (Coutré et al ., 2013). For this reason, it is important to have a common criterion for age readings and growth parameter estimations, because the differences will not allow to adequately identify temporal changes in life‐history traits within the same population.…”

Section: Discussionmentioning

confidence: 99%

“…In Argentinian and Uruguayan waters, this species occurs from shallow coastal waters to approximately 100 m depth (Cousseau et al, 2007). A. castelnaui is a predator with a narrow trophic niche breadth, feeding almost exclusively on teleost fishes (Barbini et al, 2020;Barbini & Lucifora, 2012).…”

Section: Introductionmentioning

confidence: 99%

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

Barbini

Sabadin

Román

et al. 2021

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.