The tiger shark Galeocerdo cuvier (Péron & Lesueur, 1822) (Carcharhinidae) is classified as near-threatened along the Brazilian coast, in line with its global categorization. Although Rio de Janeiro, located in southeastern Brazil, is internationally identified as a priority shark conservation area, many shark species, including tiger sharks, are landed by both industrial and artisanal fisheries in this state. However, there is a lack of detailed information on the species capture pressures and records for the state of Rio de Janeiro. Therefore, the aims of this study were to expand the tiger shark record database and to improve upon future conservation and management strategies. Tiger shark records from four coastal Rio de Janeiro regions were obtained by direct observation. The information obtained from fishery colonies/associations, environmental guards, researchers, and scientific articles, totaling 23 records, resulted in an approximately 5-fold increase in the number of tiger shark records off the coast of the state of Rio de Janeiro. A possible seasonality pattern concerning the size of the captured/observed animals was noted, emphasizing the need to consider the coast of Rio de Janeiro as an especially relevant area for at least part of the life history of tiger sharks.

Bivalves have a crucial have great social, economic, and ecological importance in coastal regions. The mussel Perna perna has a wide distribution throughout the Brazilian coast and is intensively used in farming activities. This study aims to characterize the sound emitted by mussels under laboratory conditions and estimate the variation in their acoustic activity rate according to the population density. Two groups of treatments were designed (total and partially submerged), each one with three different population densities: 10, 40, and 80 individuals. The recordings occurred in an acoustically insulated tank. A total of 4,344 acoustic activities were recorded. The sounds were associated to the valve movements and classified as impulsive activities. The acoustic activity was mainly concentrated in the 4–6 kHz band. The maximum sound pressure level (max SPL) ranged from 43 to 105 dB re 1μPa. The longest acoustic activity was detected in the class of 0.01–0.02s. According to the Kruskal-Wallis and Nemenyi tests, the acoustic activity rate was density-dependent, increasing with the mussels density. The results allowed to estimate the population density of Perna perna based on its acoustic activity which might be an important step toward the population monitoring over a spatial and temporal scale.

Mercury (Hg) is a trace metal that is considered a major contaminant of fresh and marine waters due to natural sources and anthropogenic sources such as gold mining and industrial processes. From a toxicological point of view, Hg is one of the most widely studied elements, especially in the area of food, due to its high toxicity, high absorption levels, and low excretion rates, which lead to an increase in its concentrations in the food chain. It enters the human body through the consumption of fish, posing a risk to human health. Owing to these facts, this study aimed to determine total mercury (THg) concentrations in the tuna species, little tunny (Euthynnus alletteratus), to compare the concentrations between males and females, and to analyze whether these concentrations fall within the maximum limit established by Brazilian and international legislations for predatory (carnivorous) fish, which is 1.0 mg.kg-1. In our study, the Hg concentration found in males ranged from 0.034 mg.kg-1 to 1.930 mg.kg-1, while in females it ranged from 0.036 mg.kg-1 to 1.980 mg.kg-1. The maximum values discovered were nearly twice as high as the recommendations of Brazilian and international legislations for carnivorous fish. Therefore, it is concluded that regular consumption of this species may endanger human health.

We report the first record of Pontoporia blainvillei (Gervais & d’Orbigny, 1844), Franciscana or La Plata River Dolphin, along the coast of Arraial do Cabo, southeastern Brazil. On 8 October 2017, a newborn was stranded in the surf zone of Prainha Beach and was returned to the sea. Although an occasional record, fills a distribution gap of the species’ occurrence on the coast of Rio de Janeiro state and, consequently, helps clarify the distribution pattern of P. blainvillei along the coast of the Brazil.

Globally, the growing pressure on elasmobranchs presents a significant threat. The Z-13 Fisher Colony, located in Rio de Janeiro’s metropolitan region, is composed of an urban-artisanal fishing fleet operating in a macro-area adjacent to the “Hope Spot - MoNa Cagarras” in “Rio de Janeiro Shelf ISRA”. Locally, elasmobranch fishing has been carried out for over a century. Artisanal fishery poses a potential threat to the populations of this taxon, with more than 1/3 listed globally in IUCN Red List categories. As an attempt to inform fisheries management, a Productivity Susceptibility Risk Analysis (PSA) was applied, as a locally unprecedented approach, to assess the Vulnerability of 31 landed elasmobranch species by the mentioned urban-artisanal fisheries. Analyses indicated that most small to medium-sized elasmobranch species (n = 25; 80.6%) had medium to high Productivity; while 11 (35.5%) species showed high Susceptibility to artisanal fishing. Five species showed higher Vulnerability, and were comprised by 03 sharks (S. lewini, S. zygaena, and I. oxyrinchus) and 02 rays (A. castelnaui and P. horkelii). Seven species showed medium Vulnerability being 05 sharks (S. occulta, R. porosus, C. falciformes, C. obscurus, and S. argentina) and 02 rays (D. hypostigma and P. percellens). The other 19 species (61.3%) presented lower Vulnerability and were comprised by 08 (25.8%) species of sharks and 11 (35.5%) of rays. The species identified as having high Vulnerability or potential risk should be immediately prioritized for fisheries management and administration by the Brazilian responsible agencies, to protect the potential of the taxon for ecosystem functions and prevent further extinctions.