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Simple Summary: The bluntnose sixgill shark, Hexanchus griseus, is a widely distributed species found in all oceans, even if irregularly, inhabiting continental shelves and slopes, islands, and mid-ocean ridges in deep seas. The species is currently classified by the International Union for Conservation of Nature (IUCN) as globally near-threatened, with a decreasing population. Despite some records in Brazil, the known distribution of this species in the Southwestern Atlantic is very patchy and, in some cases, not yet recorded in the world reference literature, such as in northeastern Brazil. This study, therefore, highlights new records for the species in the Tropical Southwestern Atlantic, particularly off the northeastern Brazilian coast. This information is paramount to establishing distribution maps for the species employed in a population status assessment by the IUCN. The bluntnose sixgill shark, Hexanchus griseus, is a widely distributed demersal species found in tropical and temperate waters of the Pacific, Atlantic, and Indian Oceans, inhabiting continental shelves and slopes, islands, and mid-ocean ridges at depths ranging from 200 to 1100 m. In the Southwestern Atlantic, this species has been recorded from northeastern to southern Brazil, Argentina, and Uruguay. Despite this, the known distribution of this species in the Southwestern Atlantic is very patchy and, in some cases, still mostly ignored in the literature, such as in northeastern Brazil. This study, therefore, aimed to report 23 new records of Hexanchus griseus in the Tropical Southwestern Atlantic and highlight the presence of this species off the northeastern Brazilian coast. So far, Hexanchus griseus was officially reported from the Fernando de Noronha Archipelago, Saint Peter and Saint Paul Archipelago, and the state of Ceará along the northeast coast of Brazil. Herein, the known distribution is extended to the continental shelf breaks and upper slopes of other Brazilian states, reinforcing the previously reported occurrence of the species near the Saint Peter and Saint Paul Archipelago. [ABSTRACT FROM AUTHOR]

Understanding the ecological role of species with overlapping distributions is central to inform ecosystem management. Here we describe the diet, trophic level and habitat use of three sympatric stingrays, Hypanus guttatus, H. marianae and H. berthalutzae, through combined stomach content and stable isotope (δ13C and δ15N) analyses. Our integrated approach revealed that H. guttatus is a mesopredator that feeds on a diverse diet of benthic and epibenthic marine and estuarine organisms, principally bivalve molluscs, Alpheus shrimp and teleost fishes. Isotopic data supported movement of this species between marine and estuarine environments. H. berthalutzae is also a marine generalist feeder, but feeds primarily on teleost fishes and cephalopods, and consequently occupies a higher trophic level. In contrast, H. marianae is a mesopredator specialized on shrimps and polychaetas occurring only in the marine environment and occupying a low niche breadth. While niche overlap occurred, the three stingrays utilized the same prey resources at different rates and occupied distinct trophic niches, potentially limiting competition for resources and promoting coexistence. These combined data demonstrate that these three mesopredators perform different ecological roles in the ecosystems they occupy, limiting functional redundancy. [ABSTRACT FROM AUTHOR]

Between 1992 and 2000, 681 blue sharks, Prionace glauca (173.8–310 cm total length, TL) were collected off northeastern Brazil (Brazilian EEZ). Vertebral sections of 156 males (173.8–310 cm TL) and 80 females (185.5–283 cm TL) were analysed. The index of average percentage error (IAPE) ranged from 0 to 3.1% for 3–12 growth rings (GRs). Mean marginal increment (MI) decreased from November to January without, however, conclusively confirm the annual pattern of deposition. Growth parameters were derived using the von Bertalanffy growth function (VBGF), the Richards function and the Schnute function. VBGF was that which best fit the data. Parameters derived from back-calculated lengths, K=0.157, L∞=352.1 cm and t0=−1.01 year, were considered to best describe growth. First maturity sizes of 225 cm for males and 228 cm for females corresponded to 5-GRs individuals. A 310-cm male had 12 GRs which was the highest number in the entire sample. Growth rates of 33.9 cm per GR were estimated from birth to the first band corresponding to 60.2% of size at birth, which is 56.4 cm. Adult males were 90.5% of the entire male sample and, adult females corresponded to 79.6% of the sample of females. The male sample was composed of individuals from 3 to >11 GRs and females were 3 to 10 GRs. Males were larger (with higher number of GRs) and outnumbered females in the overall sample, as commonly occurs in catches worldwide. Despite the hypothesis of differential growth by sex, postulated by several authors, the present study demonstrated that growth curves did not differ significantly, even considering significant vertebral radius (VR)–TL regressions for males and females. Higher growth rates were found in the southern Hemisphere, leading to significant differences in VBGF when compared to other areas. Discards and unreported catches are of great concern for conservation of this important apex predator. [Copyright &y& Elsevier]

Hypanus marianae, a stingray endemic to Brazil, inhabits coastal coral reef areas occurring in the landings of artisanal fisheries. The present study aimed to characterize the diet of this species captured off Pernambuco. We obtained 77 stomachs with contents: 52.27% female, 47.72% male. DW ranged from 15 to 37.80 cm mean of 26.53 ± 4.82 cm. Four higher taxonomic prey categories were identified: Arthropoda, Annelida, Chordata and Sipuncula. The most important item in the diet was Polychaeta (40.65% IRI), followed by Leptochela serratorbita (30.35% IRI), suborder Dendrobranchiata (10.18% IRI), order Isopoda (4.19% IRI), and Meiosquilla schmitti (3.56% IRI). H. marianae displays specialized predatory habit (BA = 0.06) primarily based on shrimps (42.36% IRI) and polychaetes (40.65% IRI). There was no significant difference in the diet by sex or in sexual development stages. However, neonates fed on decapods crustaceans (70.68%) and polychaetes (17.09%). For immatures, decapod crustaceans (69.5%) and polychaetes (25.86%) made up most of their diet. The adults feed mainly on polychaetes (62.79%) and crustacean decapods (30.47%), with a slight increase of fish (5.46%). The trophic level (TL) estimated was based on stomach content analysis was 3.66 and estimated on the analysis of stable isotopes being 3.29, which classified the species as a mesopredator. [ABSTRACT FROM AUTHOR]

Demand for ray consumption has been increasing considerably along coastal areas of the Western Atlantic Ocean, especially Northeast Brazil. Species previously caught as bycatch are now targeted by fisheries but the available information on these species remains scarce. In the present study, we provide the first application of stable isotopes from muscle tissue (δ13C and δ15N) and vertebrae microchemistry (24Mg, 43Ca, 55Mn, 86Sr, 138Ba) data to analyze the habitat use of batoids. We employ these techniques on three sympatric demersal stingray species across different life stages. Our approach revealed entry and exit movements in estuarine areas by Hypanus guttatus , a strong specificity for coastal reef habitats for Hypanus marianae , and the use of deeper waters by adults of Hypanus berthalutzae. We also found significant between-sex differences in habitat use for H. berthalutzae , especially for elements associated with hypoxic zones (55Mn) and salinity variations (86Sr and 138Ba), suggesting that males move to deeper areas farther from the coast during ontogeny. Both data sources employed were considered good descriptors for the various environments these species are found in. Our results suggest that mangroves and coral reefs are the most important areas for H. guttatus and H. marianae , respectively, while H. berthalutzae seems to use the entire continental shelf throughout its life cycle. We further discuss how these results may translate into each species distribution range and fishing pressure. • First application of stable isotopes and microchemistry to analyze habitat use in batoids. • The Longnose stingray demonstrates movement between estuarine and coastal environments throughout its life cycle. • Coastal reef habitat specificity in Large-eye stingray, indicating high risk of overexploitation from reef-based fisheries. • Deeper water exploration by adult Lutz's stingray suggests a broader habitat use across the continental shelf. • Sex-specific habitat use in Lutz's stingray, with males moving to deeper, offshore waters during ontogenetic development. [ABSTRACT FROM AUTHOR]