Parturition time for the Blacktip shark, Carcharhinus limbatus (Carcharhiniformes: Carcharhinidae), in Southwestern Atlantic

The determination of the period of parturition and identification of nursery areas are fundamental for the management and conservation of a fishing resource. Through combination of monthly abundance, length measurements, and development time of embryos we inferred about parturition time of the Blacktip sharks, Carcharhinus limbatus, from Southwestern Atlantic. Specimens of C. limbatus were caught from 2002 and 2008 by artisanal fleets from three different locations along the Brazilian coast using gillnets (mesh width ranging between 30 and 120 mm between opposite knots and operating from 9 to 120 m in depth), handlines (19 to 140 m depth) and longlines (6 to 90 m depth). Through a comparative analysis of fisheries landing data collected, we have verified neonatal (< 90 cm) catch peaks at specific times of the year in different locations and, matching with birth prediction of embryos, propose that C. limbatuspresents a well-defined parturition time in late spring-early summer in Southwestern Atlantic. Moreover, we indicate supposed nursery grounds for the species along the Brazilian coast. This information will be crucial for stock assessments of the species and may serve as a basis for determining fisheries management measures.(AU)

A determinação do período de parto e identificação de áreas de berçário são fundamentais para o manejo e conservação da espécie. Através da combinação de abundância mensal, comprimentos e tempo de desenvolvimento de embriões nós inferimos sobre a época de parto do tubarão galha preta, Carcharhinus limbatus, no Sudoeste Atlântico. Espécimes de C. limbatus foram capturados entre 2002 e 2008 por frotas artesanais de três locais diferentes ao longo da costa brasileira usando redes de emalhar (largura de malha variando entre 30 e 120 mm entre nós opostos e operando de 9 a 120 m de profundidade), linhas de mão (19 a 140 m de profundidade) e espinhel (6 a 90 m de profundidade). Através de análise comparativa de dados de desembarque pesqueiro, verificamos picos de captura de neonatos (< 90 cm) em períodos específicos do ano em diferentes localidades e, combinando com a previsão de nascimento de embriões, propomos que C. limbatus apresenta um período de parto bem definido no final da primavera e início do verão no Sudoeste do Atlântico. Além disto, nós indicamos prováveis áreas de berçário ao longo da costa brasileira. Estas informações serão cruciais para avaliações de estoque da espécie e poderão servir de base para determinação de medidas de manejo de pescarias.(AU)

Age structure and multi-model growth estimation of longnose stingray Hypanus guttatus (Dasyatidae: Myliobatoidei) from north-east Brazil.

We collected 729 Hypanus guttatus from the northern coast of the state of Rio Grande do Norte (RN), of which 196 were used to estimate age and growth. Ninety-five were male (12.7 to 57.0 cm disc width; WD ) and 101 were female (13.0 to 88.5 cm WD ); females were significantly larger than males. Cross sections of vertebrae showed band-pairs ranging from 0 to > 14 in females and from 0 to 9 in males. New-borns presented an opaque edge at birth in vertebrae without a birthmark. The average percentage of error (APE; %E) for the entire sample provided evidence that ages were repeatable. The mean monthly marginal increment (IM ) indicates annual band-pair formation from August to November. The annual cycle model for one band-pair deposition provided the best fit to data based on the AIC, with peaks between August and October, similar to that found in the IM analysis, suggesting an annual formation pattern. A multi-model approach that included four models based on the observed mean WD at age indicated a modified von Bertalanffy growth model as the best for describing the species growth: W0 (WD at birth) = 14.6 cm for both sexes; females W∞ = 98.61 cm (95% CI = 87.34-114.61 cm); k = 0.112 year-1 (CI = 0.086-0.148 year-1 ); males W∞ = 60.22 cm (CI = 55.66-65.35 cm); k = 0.219 year-1 (CI = 0.185-0.276 year-1 ). The age-at-maturity in males and females is 5 years and 7 years, respectively. The age composition shows that most (84%) specimens were aged 0 to 2 years. The information provided here is essential for analytical assessments of H. guttatus, which is subject to significant fishing pressure mainly on new-borns and juveniles.

Taxonomic and morphological revision of butterfly rays of the Gymnura micrura (Bloch & Schneider 1801) species complex, with the description of two new species (Myliobatiformes: Gymnuridae).

An extensive taxonomic revision of Gymnura micrura based on external and internal morphology, and considering specimens from its entire geographical distribution in the Atlantic Ocean, is presented. Gymnura micrura is redescribed and a neotype is designated; its distributional range is limited to the Southwestern Atlantic. Two new species of butterfly rays are described: Gymnura lessae, sp. nov., occurring in the North and Central Western Atlantic, and Gymnura sereti, sp. nov., found in the Eastern Central Atlantic. The three species are morphologically very similar (with G. micrura most similar to G. lessae, sp. nov.) and cannot be distinguished based on the primary diagnostic characters typically utilized for butterfly rays. The dorsal color, smaller size and eventual presence of a dorsal fin in some males may be helpful to distinguish G. micrura, whereas the size and morphology of the clasper are the main external characters separating G. sereti, sp. nov., from the other two species, although the shape of disc (especially among adult males) and contour of the lower lip are also helpful. Despite the skeleton being conservative among the species, we found consistent variations that support the validity of the new species described. Due to similarity in external morphology these internal characters were fundamental to discriminate the new species. The scapulocoracoid was an important diagnostic skeletal structure, exhibiting a series of variations that separated the three species. Variations in the synarcual, outline of the dorsal cranial fontanelle, number and shape of mesopterygia, and small differences in the mandibular arches and pelvic girdle were useful to diagnose G. sereti, sp. nov. The contour of the hyomandibula was an important diagnostic character distinguishing G. lessae, sp. nov., from the other two species. Meristic data were also useful, with G. sereti, sp. nov., presenting a lower number of radials in the second element of the mesopterygium and a higher number of diplospondylous vertebrae. In contrast, G. lessae, sp. nov., presented a higher number of pectoral-fin radials. Subtle, but consistent differences, were also found in the design of the ventral lateral-line system. A Canonical Discriminant Analysis provides strong statistical support for the validity of the new species, significantly distinguishing the three species groupings (p < 0.00001). External morphology, ventral lateral-line system and skeleton are described and illustrated for all three valid species.