No-take marine reserves (NTRs), i.e. areas with total fishing restrictions, have been established worldwide aiming to promote biodiversity and ecosystem conservation. Brazil has 3.3% of its exclusive economic zone protected by 73 different NTRs, however, most of them currently lack scientific knowledge and understanding of their ecological role, particularly regarding rocky reefs in subtropical regions. In this context, this study aimed to contrast a network of NTRs with comparable fished sites across a coastal biogeographic gradient to investigate the effect of fishing and habitat variability on the abundance and body size of rocky reef fish. We used Baited Remote Underwater stereo-Video (stereo-BRUVs) and Diver Operated stereo-Video (stereo-DOVs) systems to simultaneously sample reef fish and habitat. Model selection and results identified habitat and biogeographic variables, such as distance from shore, as important predictor variables, explaining several aspects of the fish assemblage. The effect of protection was important in determining the abundance and body size of targeted species, in particular for epinephelids and carangids. Conversely, species richness was correlated with habitat complexity but not with protection status. This is the first study using these survey methods in the Southwestern Atlantic, demonstrating how a network of NTRs can provide benchmarks for biodiversity conservation and fisheries management.

Sharks of the genus Rhizoprionodon are among the most important predators along the coastal marine ecosystems, and they represent an important economic resource for the small-scale fisheries. To properly manage and conserve exploited shark species, detailed analyses of their population structure are needed. To evaluate the gene flow and levels of the genetic diversity among populations of the Caribbean sharpnose shark R. porosus, we identified the nucleotide sequence based on collections (n = 321 specimens) from 10 different areas, including the Caribbean Sea and several locations along the entire Brazilian coast. The analysis of 802 nucleotides from the mitochondrial DNA control region revealed 53 distinct haplotypes. The majority of these haplotypes were restricted to their collection locales with a significant genetic structure detected among the overall populations (U ST = 0.237, P \ 0.0001). The data suggest a population division with two distinct management units in the western Atlantic. These management units are likely separated by the Equatorial Current. The strong population structure in R. porosus indicates that regional populations, if depleted, will not recover swiftly through immigration.

Summary This study provides information on the seasonal occurrence, length‐width relationship, sexual development and size at first maturity of the critically endangered Brazilian guitarfish Pseudobatos horkelii in southeastern Brazil. Samples were obtained from September 2007 to August 2009 from commercial fisheries off São Paulo State coast at depths of 10–50 m, with net mesh sizes of 150 mm in the main net and 100 mm in the cod end. A total of 143 specimens (71 males, 72 females) were analyzed. Total length (TL), disc width (DW), sex and reproductive variables were recorded for each individual. Pseudobatos horkelii presents sexual dimorphism in length‐width relationships, with females attaining larger TL and DW. Females also mature at a larger TL, at 81.1% of the maximum TL, while males mature at 67.8% of the maximum TL. No specimens were captured in winter, and only a small sample size was observed in autumn. Males captured in spring and summer presented semen in the seminal vesicle, indicating that this species may reproduce in the warmer months, as already observed for other Rhinobatidae as well as for P. horkelii in southern Brazil.

The night shark, Carcharhinus signatus, is a mesopelagic, semi‐oceanic shark species found only in the Atlantic Ocean. It is one of the most frequently caught sharks in pelagic longline fisheries and is classified as Vulnerable by the International Union for the Conservation of Nature (IUCN). Despite their prevalence in commercial fisheries, the population genetic structure of the night shark has not been assessed. The present study investigated the genetic diversity, genetic connectivity, and phylogeography of the species throughout the western Atlantic Ocean, based on complete mitochondrial control region (mtCR) sequence data (n = 152) and genotypic data from nine nuclear microsatellites (n = 119). The mtCR sequence revealed 19 haplotypes, with overall haplotype and nucleotide diversities of 0.74 (±0.027) and 0.0034 (±0.0019), respectively, whereas the nuclear microsatellite observed and expected heterozygosities were 0.408 and 0.421, respectively. There was significant population structure (ФST = 0.429; P < 0.01) and isolation by distance (r = 0.65, P = 0.03) based on mtCR sequence data, but no genetic differentiation based on nuclear microsatellite analyses. The phylogenetic analyses support the existence of two matrilineal lineages, which diverged during the Pleistocene. Mitochondrial demographic analyses indicated a historical bottleneck effect followed by population expansion during the Pleistocene, whereas nuclear microsatellites did not detect a recent or a strong bottleneck. For conservation purposes, we advocate that the species should be considered to comprise at least two management units (MUs) in the western Atlantic Ocean. MU‐specific catch quotas should be implemented throughout the range of the species given its low genetic diversity and vulnerability to overexploitation.

The reproductive biology of the guitarfish Rhinobatos percellens was studied from 751 specimens caught by bottom pair trawlers off the coast of São Paulo, Brazil, between c. 24° 00' S; 45° 15' W and c. 25° 10' S; 47° 52' W, from September 2007 to August 2009. The total length (L(T)) and total mass (M(T)) relationship for males and females combined was M(T) = 1·29E-06 L(T) (3·15) (r = 0·99, n = 751). The mean L(T) of sexually mature specimens was 548 mm for males and 583 mm for females. Clasper growth was allometric and showed three distinct phases. Most claspers were calcified in specimens of c. 550 mm L(T). The mean diameter of the largest oocyte was 29·8 mm, the mean ovarian fecundity was seven oocytes and ovulation occurred between August and November. Uterine fecundity ranged from two to 13 embryos (mean of five embryos). Larger females had higher litter sizes and larger embryos; the size-at-birth was c. 200 mm L(T). The hepato-somatic index oscillated seasonally for males and females; the gonado-somatic index had little variation in males, but varied seasonally in females. The presence of many non-pregnant adult females and of encapsulated eggs during two consecutive seasons suggests a resting period between gestations and the possibility of diapause.

The age and growth of three endemic threatened guitarfish species were analysed using vertebrae of Pseudobatos horkelii, P. percellens and Zapteryx brevirostris. Edge and marginal‐increment analyses were used to evaluate the periodicity of the formation of the band‐pairs, suggesting deposition of one band‐pair per year, from late winter to late spring. The von Bertalanffy growth model was used to describe the growth of these species with the following parameters, for pooled sexes: P. horkelii L∞ = 126.93, k = 0.19 and t0 = −1.51; P. percellens L∞ = 109.31, k = 0.16 and t0 = −1.78; Z. brevirostris L∞ = 60.37, k = 0.24 and t0 = −1.42. Our results are essential to understanding the resilience and vulnerability of these species to harvest, which can contribute to management and conservation actions of these species.

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The hunting tactics of lemon sharks, Negaprion brevirostris, are described from underwater and cliff-top observations in the Fernando de Noronha Archipelago, western equatorial Atlantic, Brazil. Two main tactics were observed in the shallow waters of sandy beaches and reefs environments: (i) "substrate inspection" of crevices and holes over rocky and reef bottoms, and (ii) "sardine blitz", which refer to striking schools of fishes (mainly sardines) in the surf zone. The first tactic was restricted to juveniles up to 2 m of total length, whereas subadult and adult sharks with total length larger than 2 m displayed the second. As lemon sharks use waters less than 5 m depth to hunt, perform social behaviours and predator avoidance, results highlight the importance of properly managing these habitats for their conservation, especially in areas where tourism has increased substantially.Keywords: Carcharhinidae, Elasmobranch, Foraging Behaviour, Predation, Predator-prey Interactions.As táticas de caça do tubarão-limão, Negaprion brevirostris, são descritas a partir de observações subaquáticas e de mirantes no Arquipélago de Fernando de Noronha, no Atlântico ocidental equatorial, Brasil. Duas táticas principais foram observadas em águas rasas de praias arenosas e ambientes recifais: (i) "inspeção do substrato" de fendas e cavidades em fundos recifais e rochosos e (ii) "ataques a sardinhas", que se referem a ataques repentinos a cardumes de peixes (principalmente sardinhas) na zona de arrebentação. A primeira tática esteve restrita a tubarões jovens com até 2 m de comprimento total, enquanto a segunda foi executada por subadultos e adultos com comprimento total acima de 2 m. Como os tubarões-limão utilizam águas com profundidades inferiores a 5 m para caçar, realizar interações sociais e evitar predadores, os resultados realçam a importância de se manejar adequadamente estes hábitats para sua conservação, especialmente em áreas onde o turismo tem aumentado substancialmente.Palavras-chave: Carcharhinidae, Comportamento de forrageamento, Elasmobrânquios, Interação predador-presa, Predação.