Reentrâncias Maranhenses holds the regular presence of Daggernose Shark and Wingfin Stingray as resident range-restricted species. Both species only occur in the Brazil North Shelf Large Marine Ecosystem.

Historically, between December 1989–September 1991, 1,135 Daggernose Sharks were recorded from gillnet fishery surveys. Since the 1990’s, catches have decreased in abundance by 90% (Lessa et al. 2006; Almeida et al. 2014). There are at least nine contemporary records of Daggernose Sharks in this area. Between 2018–2020, four animals were opportunistically sampled in fish markets from fishers operating within the area (Lessa & Feitosa 2021). This included the largest individual of this species ever recorded, a female measuring 148.3 cm total length (TL). The other three individuals were juveniles, measuring 76–80.5 cm TL. The average size-at-birth of this species is ~43 cm TL (Lessa et al. 2000). A young-of-the-year (YOY) Daggernose Shark was captured ~110 km from the Pindaré River mouth in December 2016 (Feitosa et al. 2020). An additional individual was captured in the area by the artisanal longline fleet between 2018–2019 (Wosnick et al. 2023); a large female measuring 122 cm TL. Further, additional records of five immature Daggernose Sharks captured in the area were shared on social media in 2023 and 2024. The species corresponded to about 10% of shark captures of the first recorded exploitation (1983–1985), reaching 71 kg/km in the second (1990–1991) (Lessa 1986; Stride et al. 1992). This area is the only known remaining area with contemporary catch records in Brazil. This area has particular importance given the species has experienced a population decline of >90% in the last three decades (Lessa et al. 2016).

Between 1997–2000, seven Wingfin Stingrays were recorded from drift gillnets and beach seine surveys. Between 2019–2024, at least 188 Wingfin Stingrays were caught by fishers with gillnets or longlines in this area. Out of these 188 individuals, 161 were sampled between 2023–2024 from 95 field sampling trips, observing landings of the small-scale commercial gillnet and longline fleet in Raposa, Maranhão state (Dias 2024). In this sampling effort, Wingfin Stingrays were present in all landings and corresponded to the second most frequently recorded ray species, after the Longnose Stingray (Dias 2024). The remaining 27 individuals were sampled opportunistically from the same fishing fleet, comprising 17 males and 10 females. This comprised one embryo, five neonates, 15 immature individuals, and four adults. Sizes ranged between 15–78 cm disc width (DW). This is one of the few known areas globally where this species is regularly and predictably observed.