ISRA FACTSHEETS
ISRA FACTSHEETS
CENTRAL AND SOUTH AMERICAN PACIFIC REGION
Nayarit Central Coast
Summary
Nayarit Central Coast is located at the entrance to the Gulf of California, Mexico. It contains remarkable biodiversity due to the variety of environments and geological features such as Isabel Island (an island of volcanic origin), mangroves, estuaries (e.g., Boca de Camichín), and sandy bays (e.g., Matanchen Bay located to the south of the port of San Blas). The area is influenced by three oceanic currents: the temperate water California Current, the warm high salinity Gulf of California Current, and the warm water Mexican Coastal Current. The seasonal changes in current and temperature produces a highly productive area. This area includes a Protected Area, Ramsar site, and Key Biodiversity Area. Within this area there are: threatened species (e.g., Pacific Sharpnose Shark Rhizoprionodon longurio); reproductive areas (e.g., Scalloped Hammerhead Sphyrna lewini); feeding areas (e.g., Whale Shark Rhincodon typus); and areas important for movement (Pacific Sharpnose Shark).
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Nayarit Central Coast
DESCRIPTION OF HABITAT
Nayarit Central Coast located in waters of the Mexican state of Nayarit and within the Pacific Central-American Coastal Large Marine Ecosystem. The area comprises Isla Isabel, Boca de Camichín, and Bahía de Matanchen. Isla Isabel, located 28 km from the coast, has a volcanic origin from ~3.5 million years ago, and is characterised by the presence of craters, cliffs, plains, depressions, and ridges (CONANP 2005). The island is relatively small (surface area = 0.82 km2, maximum length = 1.8 km, average width = 0.7 km) and is surrounded by a shallow continental platform that extends along Nayarit state, with the deepest waters to the west reaching depths of 200 m. Isla Isabel is a protected area (National Park Isla Isabel), a Ramsar site, and a Key Biodiversity Area (CONANP 2005, KBA 2022, Ramsar 2022).
The region is an oceanographic transitional zone, with marked seasonal influence of three water masses: (1) the temperate (subarctic) water California Current flowing equatorward from the northwest; (2) the warm water Mexican Coastal Current derived from the Costa Rica Current and flowing poleward close to the coast; and (3) the warm high salinity water mass coming out of the Gulf of California. The influence of these water masses is strongly altered by climatic anomalies such as El Niño and La Niña (Kessler 2006; Lavín et al. 2006). During the boreal winter and spring (December–May), the large-scale circulation is cyclonic, whereas during the boreal summer and autumn (June–November), the large-scale circulation is anticyclonic (Godínez et al. 2010; Kurczyn et al. 2012; Pantoja et al. 2012). The oceanic circulation around the islands of the area is also associated with other processes (Gómez-Gutiérrez et al. 2014), such as episodic current plumes from the continental margin (Martínez-Flores et al. 2011), benthic topography (Kurian et al. 2011), local wind-forcing (Pares-Sierra et al. 1993), coastal trapped waves of equatorial origin (Zamudio et al. 2001, 2007), and the previously mentioned oceanic currents. It is suspected that these oceanic processes affect phytoplankton biomass and primary production rates in this area in a similar way to other areas at the entrance of the Gulf of California. For example, Cabo Corrientes is characterised by three periods: a relatively intense upwelling period, with high chlorophyll-a (Chla) and primary production during the boreal spring; an upwelling relaxation period during late boreal spring-early summer, when the highest primary production values of the year are recorded; and a summer-fall period, with strong stratification and the lowest seasonal chlorophyll-a and primary production values (López-Sandoval et al. 2009).
This Important Shark and Ray Area is delineated from inshore and surface waters (0 m) to a depth of 200 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 the area. These are the Critically Endangered Scalloped Hammerhead (Rigby et al. 2019), the Endangered Whale Shark (Pierce & Norman 2016), and the Vulnerable Pacific Sharpnose Shark (Pollom et al. 2020).
According to Mexican legislation, Whale Shark is a protected species based on its vulnerability and is classified as ‘threatened’ (DOF 2007, 2010).
CRITERION C
SUB-CRITERION C1 – REPRODUCTIVE AREAS
Nayarit Central Coast is an important reproductive area for one shark species. Scalloped Hammerheads use coastal areas around Boca de Camichín and San Blas and the waters around Isla Isabel as nurseries, with neonates and young-of-the-year regularly captured in coastal areas (during the boreal summer and fall), and juveniles caught near the island (during the boreal spring) (Pérez-Jimenez et al. 2005; Tovar-Ávila et al. 2015, 2017). Around Isabel Island, 3,668 individuals were recorded from 2000–2001 with sizes between 55–135 cm total length (TL), while from 2007–2013 the majority of individuals ranged from 35.8–130.0 cm TL. Size-at-birth for this species is reported at 31–57 cm TL (Ebert et al. 2021).
CRITERION C
SUB-CRITERION C2 – FEEDING AREAS
Nayarit Central Coast is an important feeding area for one shark species. Juvenile and adult Whale Sharks use this area for feeding purposes based on satellite telemetry and direct observation (Guzman & Ketchum 2012; Ramírez-Macías et al. 2016). Yearly feeding aggregations, from October to March, prompt tourist activities around them in the Boca de Camichín area. These seasonal aggregations have been observed for more than 20 years in the area with animals feeding mostly on copepods (Ramírez-Macías et al. 2016).
CRITERION C
SUB-CRITERION C4 – MOVEMENT
Nayarit Central Coast is an important movement area for one shark species. Juvenile and adult Pacific Sharpnose Sharks move to the Nayarit Central Coast during boreal winter and then move to northern areas of Sinaloa as indicated by seasonal landing patterns of artisanal fisheries along the east coast of the Gulf of California. The full migration pattern of the species remains unknown but there are clear indications of a seasonal shift in the occurrence of this species between these sites (Pérez-Jiménez et al. 2005; Furlong-Estrada et al. 2015; Tovar-Ávila et al. 2017). During January, this species is caught near Isabel Island (Pérez-Jiménez et al. 2005), and after that, during late winter and especially during spring, fishers in southern Sinaloa (near Playa Sur) target them (Bizzarro et al. 2009). Finally, adult females move to northern areas in Sinaloa (La Reforma) to give birth and are caught by artisanal fisheries during late spring and summer (Corro-Espinosa 2011; Corro-Espinosa et al. 2011).
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