Age and growth of Zapteryx brevirostris (Elasmobranchii: Rhinobatidae) in southern Brazil

Abstract

Age and growth studies are fundamental to successful fisheries management. Zapteryx brevirostris (Müller & Henle, 1841) is distributed off the Brazilian continental shelf and this species is assessed as “Vulnerable” in the Red List of the International Union for the Conservation of Nature (IUCN). Thus, the objective of this study was to present previously unknown information about the age and growth of Z. brevirostris that can be used for its management, conservation, and fisheries. A total of 162 specimens were sampled, with total lengths (TL) varying between 35.7 cm and 56 cm. The vertebrae were embedded in resin, sectioned in cuts with 0.5 mm thickness and the growth bands of the vertebrae were read under a light microscope. In the studied area, Z. brevirostris ages were estimated from 4 to 10 years according to vertebrae patterns. The species reaches its maximum asymptotic size (Linf) around 56 cm (56 cm for females and 50.37 cm for males). This is the first estimate of age and growth for a species of the Zapteryx genus, and the results support the hypothesis that this ray requires future management conservation, particularly due to its slow growth rate and consequent susceptibility to overexploitation.

Age and growth of three endemic threatened guitarfishes Pseudobatos horkelii, P. percellens and Zapteryx brevirostris in the western South Atlantic Ocean

“…The size range observed in the sample was slightly smaller for P. horkelii than the 22.0–138.0 cm L T reported by Vooren et al . () in southern Brazil, but slightly larger (17.2–72.6 cm) L T for P. percellens (Carmo et al ., ) and 35–56 cm L T for Z. brevirostris (Carmo et al ., ) in southern Brazil. Based on the size distribution, all size classes were represented for P. percellens and Z. brevirostris ( i.e ., neonates, juveniles and adults), including near‐term embryos for Z. brevirostris .…”

“…Conversely, Carmo et al . () have reported a higher value of APE (9.71%) and CV (13.7%) for Z. brevirostris .…”

“…In terms of growth parameters, the values of L ∞ estimated for all the three guitarfish species were closer to the maximum lengths reported in southern Brazil of 135 cm L T for P. horkelii (Vooren et al ., ), 102 cm L T for P. percellens (Bornatowski et al ., ) and 56 cm L T for Z. brevirostris (Carmo et al ., ); indicating that our estimates of L ∞ were not overestimated. All three guitarfish species displayed consistencies and contrasts in their growth characteristics in south‐eastern Brazil.…”

“…In contrast, the L ∞ observed in the present study for Z. brevirostris was similar to that reported in southern Brazil by the Carmo et al . (). However, the growth coefficient observed in the present study for Z. brevirostris ( k = 0.24 year −1 ) was two times higher than the value observed by those authors in southern Brazil ( k = 0.13 year −1 ; Table ).…”

“…Despite the occurrence and distribution of these species along the south‐east to south coast of Brazil, most of the few studies undertaken to date have focused on reproduction (Abilhoa et al ., ; Batista, ; Colonello et al ., ; Lessa et al ., ; Martins et al ., ; Rocha & Gadig, ) and feeding habits (Bornatowski et al ., ; Carmo et al ., ; Marion et al ., ). The knowledge of other aspects of their basic biology, including age and growth parameters, is fairly limited and only available for P. horkelii and Z. brevirostris in southern Brazil (Carmo et al ., ; Lessa, ; Vooren et al ., ) and for P. Percellens in north‐eastern Brazil (Nunes, ).…”