true

ISRA FACTSHEETS

SOUTH AMERICAN ATLANTIC REGION

ISRA FACTSHEETS

SOUTH AMERICAN ATLANTIC REGION

Costa Branca Potiguar ISRA

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Costa Branca Potiguar ISRA

Costa Branca Potiguar

Summary

Costa Branca Potiguar is located in Rio Grande do Norte State, northeast Brazil. This area is characterised by tidal flats, estuaries, mangroves, and sandy substrates and is influenced by dunes and strong winds. Tidal currents penetrate the channels over long distances from the mouth, making the estuary water hypersaline. Within this area there are: threatened species and undefined aggregations (American Cownose Ray Rhinoptera bonasus).

Costa Branca Potiguar

Costa Branca Potiguar

DESCRIPTION OF HABITAT

Costa Branca Potiguar is located in Rio Grande do Norte State, northeast Brazil. This area is characterised by tidal flats, estuaries, mangroves, and sandy substrates and is influenced by dunes and strong winds (Da Silva Costa et al. 2022). The area experiences semidiurnal and mesotidal regimes. Freshwater input into the estuary occurs mainly during the rainy season, from March–July, but low precipitation, high temperature, and high evaporation rates result in a negative water balance. Thus, tidal currents penetrate the channels over long distances from the mouth, making the estuary water hypersaline (Da Silva Costa et al. 2022).

This Important Shark and Ray Area is benthic and pelagic and is delineated from surface waters (0 m) to 60 m based on the global depth range of the Qualifying Species globally.

CRITERION A

VULNERABILITY

One Qualifying Species considered threatened with extinction according to the IUCN Red List of Threatened Species regularly occurs in the area. This is the Vulnerable American Cownose Ray (Carlson et al. 2020).

CRITERION C

SUB-CRITERION C5 – UNDEFINED AGGREGATIONS

Costa Branca Potiguar is an important area for undefined aggregations of one ray species.

Aggregations of Rhinoptera spp. (measuring an average of ~80 cm disc width [DW]) are reported by fishers to occur regularly within the area between February–May, with animals usually swimming in schools within the Tubarão River (L Werner pers. obs. 2018–2024). Between 2023–2024, opportunistic monitoring of artisanal fishery landings occurred twice in the area. In February 2023, one aggregation of ~800 Rhinoptera spp. with animals averaging 76 cm DW was landed from gillnet fisheries. Of those, 68 individuals were analysed, and all confirmed as American Cownose Rays (L Werner unpubl. data 2023). In March 2024, an aggregation of ~250 Rhinoptera spp. was observed. Of these, 40 animals were taxonomically assessed as American Cownose Rays (L Werner unpubl. data 2024). Between 2023–2024, an additional three aggregations of 2,000–4,000 kg (no counts available) were captured by fishers, but individuals could not be identified to the species level (L Werner unpubl. data 2024). In April 2024, an additional aggregation of >300 individuals within a river in this area was recorded and shared on social media. While the American Cownose Ray and Brazilian Cownose Ray overlap in their distribution in this area, these can only be distinguished by counting the series of toothplates (Last et al. 2016). Despite the limited species-specific information available from fisher observations, across all landing site sampling events, only American Cownose Rays have been reported from this area. Furthermore, Costa Branca Potiguar is a more important area for undefined aggregations of American Cownose Rays than adjacent areas. Landings of artisanal fisheries operating at Caiçara do Norte, east of this area, were monitored monthly between September 2003–August 2004, and January 2008–July 2009. Only 14 American Cownose Rays were recorded, and no Brazilian Cownose Rays were recorded (Yokota & Lessa 2006; Lessa et al. 2015). Further information is required to determine the nature and function of these aggregations.

Costa Branca Potiguar

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