The guitarfishes Pseudobatos horkelii and Pseudobatos percellens meet the criteria for threatened status as Critically Endangered (CR) and Endangered (EN), respectively. Both species occur in the Southern Atlantic Ocean. Considering the lack of data on the genetic structure of these species, the present study evaluated the genetic variability and population structure of the P. horkelii and P. percellens in the southern region of Brazil and the northern coast of Argentina, based on sequences of mitochondrial DNA, Control Region (D-loop). Samples of P. horkelii (n = 135) were analyzed in six localities situated in Northern Argentina, along the Brazilian states’ coast. The mean of nucleotide diversity was 0.0053, the ΦST was 0.4277 and demographic analysis of P. horkelii suggests the existence of stability of the populations, with D = 0.9929, FS = 2.0155, SSD = 0.0817, R = 0.2153. In P. percellens (n = 101) were analyzed from six Brazilian localities along the coast of Santa Catarina, Paraná, and São Paulo. The mean nucleotide diversity was 0.0014 and ΦST value of 0.2921, the demographic analysis indicates a high migration rate of P. percellens among the localities evaluated, with D = 0.5222, FS = 0.3528, SSD = 0.01785, R = 0.3890.

Rapid DNA/eDNA‐based ID tools, which detect specific genetic patterns without requiring sequencing, are essential for biodiversity and wildlife trade monitoring, particularly for species of conservation concern. However, the practical application of these methods remains limited by the availability of standardised protocols, accessibility of resources, and coverage across diverse taxa. This challenge is especially pronounced for Chondrichthyes, a group heavily overexploited due to fishing and illegal trade, and with data scarcity for conservation assessments. Despite their ecological and economic importance, many species lack reference sequences in databases, as well as other molecular data and tools, hindering the development of molecular tools for species identification and trade regulation. This review synthesises the current state of rapid DNA/eDNA‐based ID tools for the detection of chondrichthyan species, including established and emerging methods. It also compiles available taxon‐specific primers to facilitate efficient species identification and recommends the most suitable methods. We identify key gaps in taxonomic and geographic coverage, emphasising the need for further research to expand these tools to under‐represented species and regions. Additionally, we highlight the importance of integrating genetic approaches into enforcement frameworks to enhance conservation strategies and regulatory compliance. By providing an accessible reference for time‐ and cost‐effective genetic monitoring, this work will support evidence‐based decision‐making and improve the practical application of rapid DNA/eDNA‐based ID tools in the conservation and management of Chondrichthyes species worldwide.

The potamotrygonins are elasmobranchs that are fully adapted to freshwater environments, and are restricted to the continental waters of South America. In northern South America, potamotrygonins inhabit the hydrographic basins that drain into the Atlantic Ocean and the Caribbean Sea, while in southern South America, the are found in the Paraná-Paraguay river basin, which drains into the Atlantic Ocean (^{Thorson et al., 1983}; ^{Carvalho et al., 2003}; ^{Rosa et al., 2010}). Ongoing research into the evolution of these fish has emphasized the need for a well-supported phylogeny that can provide systematic insights into the evolutionary processes that determined the characteristics of the potamotrygonins (^{Aschliman, 2011}).

The shark Squalus albicaudus, categorized by the International Union for Conservation of Nature red list as Data Deficient due to lack of minimal information for classification, is distributed throughout the Brazilian coast. High pressures such as overfishing and anthropic activities, as well as certain biological characteristics, including k strategists, comprise influential shark stocks reduction agents. However, genetic diversity, population structure, connectivity, and effective population size data are still limited for S. albicaudus, indicating the need for further studies. In this context, the genetic variability and population structure of S. albicaudus were investigated herein to test for panmixia. Samples were obtained from coasts of the Brazilian states of Pernambuco, Rio de Janeiro, and São Paulo along the species distribution range, and single nucleotide polymorphisms (SNPs) were assessed by the ddRADseq method. The findings revealed a panmitic S. albicaudus population, explained by certain life strategies, such as polyandry and migratory behavior. Based on the genomic findings reported herein, a single S. albicaudus population should be considered in the study area, indicating the need for specific management and conservation plans at the regional scale.

Assessing genetic structure across ocean basins is essential to understand connectivity and guide conservation in data‐deficient open‐water sharks. In this study, we examined the population genomics of Squalus cf. mitsukurii by analyzing tissue samples collected from two distant regions: California, USA (Pacific Ocean) and Pernambuco, Brazil (Southwestern Atlantic Ocean). Using double‐digest restriction site‐associated DNA sequencing (ddRADseq), we generated 33 480 939 raw reads across 28 individuals and retained 1118 high‐quality single nucleotide polymorphisms (SNPs) after stringent filtering. Genetic diversity was moderate (He = 0.211–0.244), with low inbreeding levels ( F _is = −0.005–0.106). DAPC and pairwise F _st analyses revealed moderate genetic structure, indicating limited gene flow between the sampled populations. This study provides the first genomic evidence of population differentiation in S. cf. mitsukurii across these regions. Our findings underscore the importance of genome‐wide data and informing regionally conservation strategies, especially for exploited species commonly misidentified in commercial landings and lacking population management.