ISRA FACTSHEETS
ISRA FACTSHEETS
CENTRAL AND SOUTH AMERICAN PACIFIC REGION
Mulegé–Santa Rosalía
Summary
Mulegé–Santa Rosalía is located in the central Gulf of California, Mexico. This area has a very narrow continental shelf with rocky shores, sandy substrates, and mangrove ecosystems. It includes one Key Biodiversity Area and one Marine Protected Area. Within this area there are: threatened species (e.g., Spadenose Guitarfish Pseudobatos buthi); range-restricted species (e.g., Grey Smoothhound Mustelus californicus); and reproductive areas (e.g., Grey-spotted Guitarfish Pseudobatos glaucostigmus).
Download factsheet
Mulegé–Santa Rosalía
DESCRIPTION OF HABITAT
Mulegé-Santa Rosalía is located in the central Gulf of California in the Baja California Sur state of Mexico. It represents the transition zone between the northern and southern regions of the gulf and is situated within the Gulf of California Large Marine Ecosystem (LME). It sits to the east of the Guaymas basin and includes many islands, including Tortuga, Santa Inez, Coyote, and San Marcos (Robles & Marinone 1987). Within the area, the continental shelf is very narrow with the slope occurring 10 km from the shore at the widest part of the shelf. This area has a strong seasonality of sea surface temperature ranging between ~16–17°C (February–March) to 31°C (August).
Productivity is the result of the boreal summer upwelling events, due to southeast winds from July to October (Álvarez-Borrego 1983; Álvarez-Borrego & Lara-Lara 1991). However, the effect of winds and upwellings is considered weak because of the significant stratification that occurs in the water column, as well as the entry of warm, nutrient-poor tropical surface water (Álvarez-Borrego 1983; Badan-Dangon et al. 1985; Álvarez-Borrego & Lara-Lara 1991; Santamaría-del-Angel et al. 1999). Mulegé-Santa Rosalía has the only river in this area, the Mulegé River, which discharges into Bahía Concepción. This area overlaps with one Marine Protected Area, the Flora and Fauna Protection Area Islas del Golfo de California (CONANP 2000), and one Key Biodiversity Area, Isla San Marcos (KBA 2022).
This Important Shark and Ray Area is delineated from inshore and surface waters (0 m) to a depth of 1,500 m based on the bathymetry of the area.
CRITERION A
VULNERABILITY
Three Qualifying Species considered threatened with extinction according to the IUCN Red List of Threatened SpeciesTM regularly occur in this area. Threatened sharks comprise the Vulnerable Pacific Sharpnose Shark (Pollom et al. 2020a); threatened rays comprise the Vulnerable Spadenose Guitarfish (Rigby & Derrick 2021) and Grey-spotted Guitarfish (Pollom et al. 2020b).
CRITERION B
RANGE RESTRICTED
Mulegé-Santa Rosalía holds the regular presence of Cortez Skate, California Butterfly Ray, Grey Smoothhound, Bat Ray, Spadenose Guitarfish, and Banded Guitarfish as resident range-restricted species. These species are regularly encountered and caught in local fisheries (Bizzarro et al. 2009; Castro-Díaz 2021; Felipe Galván-Magaña unpubl. data 2022). Cortez Skate and Spadenose Guitarfish are endemic to the Gulf of California LME, while California Butterfly Ray, Grey Smoothhound, Bat Ray, and Banded Guitarfish are restricted to the California Current LME and the Gulf of California LME.
Cortez Skate was not reported in the main catch characterisation of artisanal shark fisheries in the area undertaken between 1998–1999 (Bizzarro et al. 2009). However, recent monitoring suggests that fisheries have extend their activities to deeper areas with rays as target species and this species in commonly landed in low numbers (Felipe Galván-Magaña unpubl. data 2022).
California Butterfly Ray was reported as an important species in landings around the area between 1998–1999, especially during the winter (Bizzarro et al. 2007). Recent monitoring data from the area confirms that this species is one of the main species in landings, mostly during the winter and summer (Castro-Díaz 2021; Felipe Galván-Magaña unpubl. data 2022).
Grey Smoothhound is part of the smoothhound complex, which represented ~3% of total shark landings in the area between 1998–1999 with the majority occurring during spring (Bizzarro et al. 2007). Recent data monitoring data from the area confirms that this species is commonly landed (Felipe Galván-Magaña unpubl. data 2022).
Ongoing monitoring of artisanal fisheries in the area indicates that Bat Ray is an important species in landings (Felipe Galván-Magaña unpubl. data 2022).
Shovelnose Guitarfish was reported as one of the most landed species during summer 1998–1999 (Bizzarro et al. 2009), but there is a high chance that these catches were comprised of Spadenose Guitarfish, a species that was recently described from the area (Rutledge 2019). According to recent monitoring in the area, Spadenose Guitarfish is one of the two most landed shark species (Pérez-Durán 2021; Soto-López et al. 2021; Felipe Galván-Magaña unpubl. data 2022).
Banded Guitarfish was reported with regular but low catches between 1998–1999 (Bizzarro et al. 2009) and recent monitoring in the area confirms that the species is still landed in low numbers (Felipe Galván-Magaña unpubl. data 2022).
CRITERION C
SUB-CRITERION C1 – REPRODUCTIVE AREAS
Mulegé-Santa Rosalía is an important reproductive area for one shark and two ray species.
From 201 Pacific Sharpnose Sharks sampled from artisanal fisheries between 2018–2019, 73% were females, of which 72% were pregnant. Embryos at different stages of development were found year-round suggesting that the complete gestation period occurs within this area. During the month of August, embryos at the first stages of development were found and the largest embryos were reported for April, however, these were not near-term embryos. A shark fishing ban in the Mexican Pacific is in place between May–July, so no samples can be obtained during these months. However, all previous findings suggest that birthing occurs during this period (Chávez-Siles 2021).
California Butterfly Ray was one of the main landed species between 2017–2020, and pregnant females have been identified in this area with embryos at different development stages. This indicated the importance of this area for the gestation of this species. Near-term embryos have been reported during February and November (Felipe Galván-Magaña unpubl. data 2022).
Grey-spotted Guitarfish is the most landed species in artisanal fisheries from this area. From 287 individuals sampled between 2017–2020, 90% were females with 99% of those pregnant. Embryos at different development stages were found between October–August and uterine eggs were recorded year-round, suggesting the occurrence of embryonic diapause. It is likely that the complete gestation cycle occurs in this area. Terminal embryos were found in October, which suggests that females give birth to neonates in this area, but the selectivity of the fishing gears used prevents the confirmation of the presence of these neonates (Martínez-Riveaux 2021).
Download factsheet
SUBMIT A REQUEST
ISRA SPATIAL LAYER REQUEST
To make a request to download the ISRA Layer in either a GIS compatible Shapefile (.shp) or Google Earth compatible Keyhole Markup Language Zipped file (.kmz) please complete the following form. We will review your request and send the download details to you. We will endeavor to send you the requested files as soon as we can. However, please note that this is not an automated process, and before requests are responded to, they undergo internal review and authorization. As such, requests normally take 5–10 working days to process.
Should you have questions about the data or process, please do not hesitate to contact us.
