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ISRA FACTSHEETS

CENTRAL AND SOUTH AMERICAN PACIFIC REGION

ISRA FACTSHEETS

CENTRAL AND SOUTH AMERICAN PACIFIC REGION

Northern Gulf of California ISRA

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Northern Gulf of California ISRA

Northern Gulf of California

Summary

Northern Gulf of California is located on the Pacific coast of Mexico. Situated at the northern end of the gulf, it extends from the Colorado River Delta in the north to the large islands of Tiburón and Angel de la Guarda in the south. The area overlaps with an Ecologically or Biologically Significant Marine Area and includes one protected area, three Ramsar sites, and three Key Biodiversity Areas. The area has a broad continental platform mostly composed of sandy substrates. The shallow waters are constantly influenced by extreme tides, strong winds, and upwellings to create the most productive region in the entire gulf. Within this area there are: threatened species (Whale Shark Rhincodon typus); range-restricted species (e.g., Peppered Catshark Galeus piperatus); reproductive areas (e.g., Brown Smoothhound Mustelus henlei); feeding areas (e.g., Shovelnose Guitarfish Pseudobatos productus); and areas important for movement (e.g., Whale Shark).

Northern Gulf of California

Northern Gulf of California

DESCRIPTION OF HABITAT

Northern Gulf of California is located along and off the coasts of Baja California and Sonora, Mexico. Situated within the Gulf of California Large Marine Ecosystem (LME), it extends from the Colorado River Delta in the north to the large islands of Tiburón and Angel de la Guarda in the south, with an average depth of 200 m (Morales-Zárate et al. 2004). The shallow waters of the Northern Gulf of California are constantly influenced by extreme tides, strong winds, and upwellings to create the most productive region in the entire gulf (Lavín & Marinone 2003). In this area, tidal mixing and turbulence occur year-round, advecting nutrients into the mixed layer and generating high productivity (Lavín & Marinone 2003). The area has high seasonality, with sea surface temperatures reaching 31–32°C in August and September, dropping to 15–17°C in January and February. The principal surface circulation of the Northern Gulf of California consists of a cyclonic (counterclockwise) gyre in the summer (June to September), and a weaker anticyclonic (clockwise) gyre from November to March. Currently, with a lack of direct input from the Colorado River to the Gulf of California (and overall high evaporation rates), the upper gulf is the equivalent of an inverse (negative) estuary, with salinities between 35–37 PSU (Lavín et al. 1998; Lavín & Marinone 2003).

This area includes one Ecologically or Biologically Significant Marine Area (EBSA), the Upper Gulf of California Region (CBD 2016). It also contains one protected area, the Biosphere Reserve Alto Golfo de California y Delta del Río Colorado (CONANP 2007), three Ramsar sites, Humedales de Bahía San Jorge, Humedales de Bahía Adair, and Humedales del Delta del Río Colorado (Ramsar 2002a, 2022b, 2022c). In addition, includes three Key Biodiversity Areas, Alto Golfo de California, Bahía e Islas de San Jorge, and Sistema San Luis Gonzaga (KBA 2022a, 2022b, 2022c).

This Important Shark and Ray Area is delineated from inshore and surface waters (0 m) to a depth of 281 m based on the depth ranges of Qualifying Species in the area.

CRITERION A

VULNERABILITY

The one Qualifying Species within the area is considered threatened with extinction according to the IUCN Red List of Threatened SpeciesTM. The Whale Shark is assessed as Endangered (Pierce & Norman 2016).

CRITERION B

RANGE RESTRICTED

Northern Gulf of California holds the regular presence of Peppered Catshark, White-margin Fin Smoothhound, Grey Smoothhound, Cortez Skate, and California Butterfly Ray as resident range-restricted species. These species are commonly caught by artisanal and industrial fisheries in the area (Santana-Morales et al. 2005; Godínez-Padilla & Castillo-Géniz 2016; Saldaña-Ruiz et al. 2016, 2017). Both smoothhounds and California Butterfly Ray are restricted to the California Current LME and the Gulf of California LME, while Peppered Catshark and Cortez Skate are endemic to the Gulf of California LME.

CRITERION C

SUB-CRITERION C1 – REPRODUCTIVE AREAS

Northern Gulf of California is an important reproductive area for two shark and one ray species.

Gravid Grey Smoothhound females have been reported with embryos in different stages of development. These gravid females were found during six non-consecutive months of the year, suggesting that the whole gestation occurs within the area. Terminal embryos ~30 cm total length (TL), which are closer to the reported size-at-birth (20–30 cm TL; Ebert et al. 2021), were present in March and April, suggesting that this is a pupping area with births occurring between April and May. Postpartum females (n = 6) were recorded during these latter months (Pérez-Jiménez & Sosa-Nishizaki 2010). This species is caught throughout the year in the region at depths between 6–265 m, but ~90% of sharks caught, including gravid females, were caught at depths < 80 m in the northern part of the area. Based on an analysis of landings, this species is still one of the most abundant species in landings from the area (Godínez-Padilla & Castillo-Géniz 2016). The whole reproductive cycle of the Brown Smoothhound occurs in the area. Two hundred and nineteen pregnant Brown Smoothhounds were examined between 2002–2004 confirming their regular presence in the area. These individuals originated from bycatch of artisanal fisheries, where they are caught year-round. Embryos in the first stages of development were found between April and June, embryos in the middle of their development between November–March, while terminal embryos were found between February and March, with births occurring from the end of February to May. Terminal embryos (25.5–28 cm TL) were close to the reported size-at-birth for the species (19–30 cm TL; Ebert et al. 2021). Females with terminal embryos were recorded at depths > 80 m (Pérez-Jiménez 2006). Based on fisheries monitoring, this species is still one of the most abundant in landings from the area (Godínez-Padilla & Castillo-Géniz 2016; Saldaña-Ruiz et al. 2017).

Shovelnose Guitarfish use the area for pupping, and the whole gestation occurs within the area. Pregnant females (n = 650) with embryos in different stages of development are targeted by fisheries year-round with higher catches occurring April-June. From August to March, uterine eggs are commonly found with no embryonic growth, followed by a fast embryonic growth during April-July, suggesting embryonic diapause of nine months. Terminal embryos (15.2–19.2 cm TL) around the reported size-at-birth (17.5 TL; Márquez-Farías 2007) are found in June when pupping occurs (Romo-Curiel 2007; Romo-Curiel et al. 2016). This is the most abundant species in landings from the area, according to recent studies (Saldaña-Ruiz et al. 2016; Medina-Trujillo 2021).

CRITERION C

SUB-CRITERION C2 – FEEDING AREAS

Northern Gulf of California is an important feeding area for one shark and one ray species.

Whale Sharks predictably aggregate in San Luis Gonzaga Bay each year from May to October. The aggregation is composed of juveniles that are constantly feeding on the surface, mainly on seasonally abundant copepods (Ramírez-Macías et al. 2012, 2016; SEMARNAT 2018).

Stomach content analysis (with samples taken from 2002–2007), showed that 77% of stomachs from Shovelnose Guitarfish were full. Individuals analysed fed mostly on crustaceans (order Decapoda and family Caridea) and small fishes (family Mictophidae; De la Rosa-Meza 2012).

CRITERION C

SUB-CRITERION C4 – MOVEMENT

Northern Gulf of California is an important area for the movement of one shark species. Whale Sharks move into the Northern Gulf of California as part of their migration route from other areas inside the Gulf of California. Based on photo-identification of 23 individuals, movement between San Luis Gonzaga and Bahía de los Ángeles has been confirmed. Furthermore, 133 individuals moved between all the aggregation sites within the Gulf of California: San Luis Gonzaga Bay, Bahía de los Ángeles, La Paz Bay, and Nayarit (Ramírez-Macías et al. 2012, 2016; Whitehead et al. 2019; SEMARNAT 2018; Pancaldi et al. 2019).

Northern Gulf of California

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