Fishes of the genus Eleotris present highly conserved morphology, which may make their recognition difficult. Here, two cryptic Eleotris lineages from five locations along the coast of Brazil were identified using the COI gene and two nuclear fragments. High bootstrap and posteriori values supported those lineages, and the genetic distance of COI varied from 6% between the two lineages to 14.1% from other western Atlantic Eleotris species, such as E. pisonis, E. amblyopsis and E. perniger. The reciprocal monophyly for both types of markers, the divergences between those lineages and the other Eleotris species from the Brazilian coast may, in fact, represent two new cryptic species. The cryptic lineages and currently recognized species were collected in distinct environments, reinforcing the need for further sampling to understand the real distribution of each taxon.

Deltas are dynamic and productive systems of enormous ecological significance, encompassing unique and biologically diverse wetland habitats. Here, we present the first data on the molecular diversity of the fish fauna of the Parnaíba Delta, the largest deltaic formation of the Americas. Partial sequences (626 bp) of the mitochondrial COI gene (Cytochrome c oxidase subunit I) were used to barcode 402 individuals, representing 128 species, belonging to 98 genera, 57 families, 17 orders and two classes. The most abundant orders were the Perciformes, Siluriformes, Gobiiformes, and Pleuronectiformes. The Neighbor-Joining (NJ), Bayesian Inference (BI), and BIN analyses produced 103 molecular clusters, while the Automatic Barcode Gap Discovery (ABGD) and Maximum Likelihood (ML) approaches revealed 102 clusters. The mean conspecific, congeneric and confamilial genetic distances were 0.33%, 14.37%, and 18.60%, respectively. Intraspecific divergence ranged from 0.0% to 1.4%, and all species presented barcode gaps, with the exception of two clusters of Cathorops spixii (OTU 96 and OTU 103), which were separated by a low interspecific distance (1.2%), which overlaps the maximum intraspecific genetic distance (1.4%). The barcode data provide new insights into the fish diversity of the Parnaíba Delta, which will be important for the development of further research on this fauna.

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Trawling is a controversial fishing method due to the perceived lack of selectivity of the net and the resulting capture of a large quantity and diversity of non-target species. Here, we used DNA barcode methods to identify the composition of the bycatch produced by the trawl fishery of the Brazilian North coast. A total of 182 species belonging to 18 orders and 62 families were captured, including 17 species under some degree of threat in the wild according to the IUCN Red List of Threatened Species (IUCN). These results highlight the impact on the marine biodiversity of northern Brazil caused by the bycatch of small-scale industrial and unregulated fishery operations, and support the application of DNA-based methods for the identification of the bycatch species taken by data-poor fisheries, as a powerful tool for the improvement of the quality of fishery catch statistics and more precise bycatch records.

Fisheries and Aquaculture are among the most popular activities in coastal regions of the world. In addition, both correspond to high-risk activities within a climate change context as they are vulnerable to environmental changes that threaten the socio-economic sustainability of the fishing communities that depend on fish for food security and income generation. In 2019, the central part of Mozambique was hit by two unprecedented cyclones: Idai and Kenneth that killed over 600 people and left nearly 2.2 million people in need of urgent assistance. The aim of the present study was to investigate the impacts these cyclones had on fisheries and aquaculture in the provinces of Sofala and Zambézia in Mozambique. The study further seeks to propose strategies that could be adopted by the communities to minimize the risks in the future. For the construction of the database, both secondary and primary data collection approaches were used to characterize the cyclone events. Secondary data was collected through sector reports and previously published articles, while primary data was collected through interviews with fishers, sector employees, and aquaculture producers in the affected provinces. The results revealed that these natural events had both a direct and indirect impact on fishing, as they affected more than 1,440 fishermen that lost 590 vessels, 1,800 fishing gear, and 67 boat engines in Sofala province. In Zambézia province, aquaculture producers lost 169 fish ponds, two cages, and 606,000 lost fry, while in Sofala province, 58 fish tanks, 204 cages, and 257,500 fish fry were lost. Overall, our study reveals the vulnerability of fisheries and aquaculture to extreme events particularly the cyclones in Mozambique. Lack of knowledge regarding climate change, advanced preventive measures, and poor adaptive capacity makes the sectors more vulnerable to disasters. Therefore, it is recommended to improve awareness programs, introduce measures and policies that promote resilience and optimum adaptive efficiency.

Summary Species with wide geographic distributions can consist of different lineages or even of different species. The present study evaluated the molecular diversity of the family Eleotridae by analyzing sequences of the COI gene from species collected in different locations in a Neotropical region as well as sequences from BOLD and GenBank. The analysis revealed the distinction and differentiation of a variety of species with high statistical support, including Gobiomorus dormitor (two lineages), Dormitator maculatus (three lineages) and Eleotris fusca (three lineages), and a number of different lineages of Microphilypnus. This indicates the existence of a number of unknown cryptic species that have not been reported previously, increasing the potential diversity of eleotrid species in the Neotropics.

This study presents the first record of Elops smithi for northern Brazil. The evidence suggests this species is being misidentified incorrectly as Elops saurus in estuaries of the Western Atlantic Ocean. Here, morphological, molecular, and cytogenetic evidence identified all ladyfish specimens from one estuary in the region as E. smithi. Thus, at least Elops smithi occurs in the northern coast of Brazil and it is recommended that specimens from this region identified as E. saurus be further investigated with genetic and cytogenetic tools in order to assure a correct species identification.

Elasmobranchs represent a well-defined group, composed of about 1,150 species inhabiting diverse aquatic environments. Currently, several of these species have been classified as threaten due to overexploitation. Therefore, we used DNA barcode to identify traded species of sharks and stingrays in the municipality of Bragança (Amazon coastal region), a major fishery landing site in northern Brazil. We collected a total of 127 samples labeled into 24 commercial nomenclatures over 1-year period. Twenty species were discriminated and 13 of them are recognized under some threatening status. In relation to sharks, Carcharhinidae showed the highest number of species, half of them classified as endangered, followed by hammerhead sharks (Sphyrnidae), with four species also regarded as threatened with extinction. The Rhinopteridae and Dasyatidae rays were the most abundant groups, with trade records of the following threatened species: Rhinoptera brasiliensis, Rhinoptera bonasus, Hypanus berthalutzae, and Fontitrygon geijskesi. It is noteworthy that threatened species of elasmobranchs have been frequently and regularly exploited because of inefficient fishery management policies. Therefore, effective inspection practices need to be incorporated in fisheries, including the use of DNA barcode to enable a reliable method of species authentication and to assure the proper commercialization.