Despite carrying an unfair burden of being considered the "great villains of the seas", sharks, along with rays and chimaeras, play vital roles in aquatic ecosystems all over the planet. These animals belong to the class Chondrichthyes (cartilaginous fish) - subclass Elasmobranchii (sharks and rays) and Holocephali (chimaeras) - and are among the most evolutionarily successful vertebrates, with a life history that began around 400 million years ago (MARANHO; BALDASSIN, 2014). Around the world, approximately 1,200 species of elasmobranchs have been described (NELSON apud ICMBio, 2016), while around 211 are known in Brazil, including marine and freshwater species (GADIG et al. in BRASIL, 2023).
Among the sharks and rays that inhabit Brazilian marine waters, some species stand out for their ecological importance and significant presence in different habitats. Sharks such as the Nurse shark (Ginglymostoma cirratum) (figure 1A) and the Sand tiger shark (Carcharias taurus) (figure 1B) are seen along the Brazilian coast and do not pose a great risk to human life, with very few records of attacks. Individuals of these species can be found under human care in Brazilian aquariums, along with some species of rays that also occur in the wild, such as the Cownose ray (Rhinoptera bonasus) (figure 1C) and the Spotted eagle ray (Aetobatus narinari). It is also worth mentioning some species that live or travel in freshwater environments, such as the rays of the Potamotrygonidae family, which live exclusively in these places, or the flathead Bull shark (Carcharhinus leucas), which is considered a marine species that makes incursions into freshwater.
The variety of species of these fascinating animals implies individuals with their own characteristics and conservation challenges. Northern Brazil is considered a global hotspot for elasmobranchs (WOSNICK et al., 2019), meaning that it is a place with a high biodiversity of animals of this class. Species such as the Daggernose shark (Isogomphodon oxyrhynchus) (figure 1D), classified as Critically Endangered (CR) on the IUCN Red List due to the high incidence of incidental capture in artisanal fisheries, are endemic to the coastal waters north of South America (LESSA apud WOSNICK et al., 2019). A few decades ago, the consumption of shark and ray meat was restricted to coastal and riverside populations, however, with the reduction of fish stocks, the consumption of this meat has become more widespread and appreciated (MARANHO; BALDASSIN, 2014). Along with the increase in hunting for the sale of delicacies such as shark fins, other anthropogenic actions also threaten the integrity of elasmobranchs, such as the degradation of coastal environments, accidental capture (by-catch), increased fishing effort and the species' own life strategy (CAMHI et al. apud LESSA et al., 1999).
Faced with these challenges, it is essential to implement effective conservation actions to protect elasmobranch populations in Brazil and around the world. The National Action Plan for the Conservation of Sharks and Rays (PAN Sharks) is an important initiative in this regard, aimed at promoting the conservation and sustainable management of these animals. The PAN Sharks establishes guidelines and strategies to protect vulnerable species, reduce incidental catches and monitor elasmobranch populations throughout the country. In addition, other conservation measures include the creation and expansion of marine protected areas, the implementation of stricter regulations for commercial fishing and raising public awareness about the importance of elasmobranchs to aquatic ecosystems (BRASIL, 2023), considering that they are animals that act in the population control of waters, regulating invasive species and maintaining balance in food chains, perform nutrient cycling, help maintain the health of coral reefs and are excellent bioindicators of the health of these ecosystems.
With all the ecological importance that revolves around the mere existence of these animals, their presence in the waters is purely beautiful. In their most varied shapes, with their unique hydrodynamics and diverse behaviors, these millenary beings are fascinating in the eyes of anyone who cares enough to get to know them, and all professionals in the field have an educational role to play with the promise of acting in favor of conservation. After all, according to the Senegalese forestry engineer Baba Dioum (1968), we will only conserve what we love, we will only love what we understand and we will only understand what we are taught.
Figure 1. A) Nurse shark (Ginglymostoma cirratum) at the Rio de Janeiro Marine Aquarium; B) Sand tiger shark (Carcharias taurus) at the Rio de Janeiro Marine Aquarium; C) Cownose ray (Rhinoptera bonasus) photograded at Océanopolis Brest (FRA); D) Daggernose shark (Isogomphodon oxyrhynchus) collected in Suriname by the Naturalis Biodiversity Center.
Fonts: 1A. Collection of the Rio de Janeiro Marine Aquarium; 1B. Collection of the Rio de Janeiro Marine Aquarium; 1C. Wikipedia site, 2012; 1D.Collection of the Naturalis Biodiversity Center.
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