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ISRA FACTSHEETS

EUROPEAN ATLANTIC

ISRA FACTSHEETS

EUROPEAN ATLANTIC

Monte da Guia ISRA

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Monte da Guia ISRA

Monte da Guia

Summary

Monte da Guia is located on the southeast coast of Faial Island in the Azores, Portugal. This area encompasses the surrounding waters of the Monte da Guia volcanic crater, including high to moderately exposed zones and sheltered areas with a diversity of coastal habitat types such as rocky reefs, vertical walls, bolder fields, gravel, rhodoliths, and sandy substrates. Within this area there are: threatened species (e.g., Common Eagle Ray Myliobatis aquila); reproductive areas (Common Stingray Dasyatis pastinaca); and undefined aggregations (Common Eagle Ray).

Monte da Guia

Monte da Guia

DESCRIPTION OF HABITAT

Monte da Guia is located on the southeast coast of Faial Island in the Azores, Portugal. This area encompasses the surrounding waters of the Monte da Guia volcanic crater, including high to moderately exposed zones and sheltered areas with a diversity of coastal habitat types such as rocky reefs, vertical walls, bolder fields, gravel, rhodoliths, and sandy substrate (EEA 2025). Entre-Montes Bay in the northeast corner and Porto Pim Bay in the northwest corner are sheltered, low energy habitats bounded by high-energy, structurally complex habitat where strong tidal currents pass through vertical walls and boulder fields (Afonso et al. 2008).

This Important Shark and Ray Area is benthic and pelagic and is delineated from inshore and surface waters (0 m) to 80 m based on the bathymetry of the area.

CRITERION A

VULNERABILITY

Two Qualifying Species considered threatened with extinction according to the IUCN Red List of Threatened Species regularly occur in the area. These are the Critically Endangered Common Eagle Ray (Jabado et al. 2021a) and the Vulnerable Common Stingray (Jabado et al. 2021b).

CRITERION C

SUB-CRITERION C1 – REPRODUCTIVE AREAS

Monte da Guia is an important reproductive area for one ray species.

Between 1997–2023, yearly underwater visual census (UVC) surveys (straight line 50 x 5 m transects parallel to the coast over rocky and sandy substrate at depths between 10–25 m) were conducted during the boreal summer around all islands of the Azores Archipelago (n = 2,509 surveys). Common Stingrays measuring <32 cm disc width (DW) were observed in 4.8% of surveys within this area (in the outer section of Porto Pim Bay; n = 27 of 554 surveys). Outside this area, the frequency of occurrence was 1.7% (n = 35 of 1,955 surveys). When only considering UVCs conducted on sandy substrate, Common Stingrays of this size were observed in 30% of the surveys. The maximum number of individuals <32 cm DW per survey within this area was three, while outside this area, all individuals were larger. Young-of-the-year (YOY) Common Stingrays measure ~30 cm DW in the northeastern Mediterranean Sea (Yeldan et al. 2009). Another survey conducted annually between 2009 and 2012 using snorkel UVCs inside the bay (three parallel lines across the bay: one in shallow waters, another in the middle, and a third in the outer portion, over sandy substrate) showed an average 2.5 stingrays per transect, 90% of measured <30 cm DW (P Afonso unpubl. data 2025).

During July–August 2021, 27 individuals (ranging 17.6–60.0 cm DW) were captured using scoop nets while freediving and tagged with external acoustic tags. Of those, 10 were <29 cm DW (37%). Individuals were tracked for up to 172 days using the surrounding receiver array (P Afonso unpubl. data 2021–2022). Tagged Common Stingray detections were restricted to five of the 15 acoustic stations around Faial and Pico, nearly all within the Monte da Guia area, especially in the Porto Pim Bay side. The weighted residency index (IWR) inside the Monte da Guia area was generally high, with ~74% of individuals exhibiting an IWR >0.75 (mean ± standard deviation = 0.82 ± 0.26). The 10 tagged juveniles (17.6–29 cm DW) exhibited particularly elevated residency throughout the summer months with an average IWR of 89% (range, 61–100%) within the area (P Afonso unpubl. data 2021). Additionally, local ecological knowledge (LEK) interviews were conducted with fishers, maritime tourism operators, and other ocean users on Faial Island in 2021 (n = 22). Respondents (n = 5; 23% of interviews) indicated that this area had the highest reported sightings of stingrays. Of these, four interviewees mentioned that the area was particularly important for small individuals (<30 cm DW) (Soares 2021).

CRITERION C

SUB-CRITERION C5 – UNDEFINED AGGREGATIONS

Monte da Guia is an important area for undefined aggregations of one ray species.

During August 2014, while conducting regular fish visual surveys, an aggregation of ~30 Common Eagle Rays was observed within this area (Afonso & Vasco-Rodrigues 2015). Following the first sighting, another six dedicated dives were undertaken until November (totalling seven dives). The aggregation (20–30 individuals; 30–90 cm DW) was observed on four dives from 8–14 August 2014. Dives in September (n = 2) and November (n = 1) had no records of the species. All individuals appeared to be females as no claspers were observed (Afonso & Vasco-Rodrigues 2015). Since then, aggregations of 5–30 individuals within this area have been reported on social media (n = 4 between 2017–2019), and dive operators report these aggregations regularly during the summer.

Additionally, from 2,515 UVC surveys conducted between 1997–2023, the frequency of occurrence in this area was 1.8% (10 of 554 transects), while outside this area it was 0.7% (15 of 1,955 transects) with a maximum of two Common Eagle Rays per transect (Afonso et al. 2018; P Afonso unpubl. data 2020–2021). Aggregations are predominantly found in the vicinity of the caves surrounding the Monte da Guia area but individuals are also observed over the adjacent sandy flats, including some neonates/YOY (~10–15 cm DW) in Porto Pim Bay during the summer (P Afonso unpubl. data 2020–2021). In the northwestern Mediterranean Sea, Common Eagle Ray breeds in August and September matching the seasonal occurrence of aggregations in this area (Capapé et al. 2007). Further information is required to understand the nature and function of these aggregations.

Monte da Guia

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