Zona Marina de la Isla Isabel

Zona Marina de la Isla Isabel National Park protects the marine waters surrounding Isla Isabel, a small volcanic island 68 kilometers northwest of San Blas in Nayarit state. The marine zone complements the island national park established in 1980 by extending federal protection to the productive reef, open-water, and pelagic habitats in the surrounding sea. The marine park designation recognizes that the extraordinary wildlife of Isla Isabel—including blue-footed boobies, California sea lions, and olive ridley sea turtles—depends critically on the health of the surrounding marine ecosystem for food and breeding resources.

The marine zone hosts the same spectacular wildlife found around the island itself. California sea lions (Zalophus californianus) hunt fish in the surrounding waters and use island rocks as haul-out sites. Blue-footed boobies (Sula nebouxii) plunge-dive for fish in the waters immediately around the island—the clarity of the water makes their underwater pursuit of fish visible from the surface. Whale sharks (Rhincodon typus) are seasonal visitors in the warmer months. Manta rays and mobula rays aggregate seasonally. Olive ridley sea turtles nest on the island beach from June to November. Hammerhead sharks and silky sharks inhabit deeper offshore waters.

The marine ecosystem is characterized by productive tropical Pacific reef communities in the shallower nearshore waters and open-ocean pelagic systems in the surrounding sea. Coral communities include Pocillopora branching corals, encrusting Porites, and various soft corals. The reef structure provides habitat for moray eels, parrotfish, and reef fish assemblages. Kelp does not occur at this latitude; instead, macroalgae including Sargassum, Halimeda, and coralline algae dominate the benthic community. Phytoplankton blooms driven by coastal upwelling fuel the food chain supporting the island's seabird and sea lion populations.

The Isla Isabel marine zone encompasses the submerged flanks and surrounding seafloor of the volcanic island. The island rises from a relatively shallow coastal shelf, with the seafloor deepening from approximately 20 meters around the island to over 100 meters a few kilometers offshore. The underwater terrain includes submerged basalt lava formations, rocky reefs, and sandy flats. The marine zone is on the eastern margin of the Pacific Ocean, influenced by the California Current bringing cold, productive water south and mixing with warmer tropical water from the south—creating a highly productive oceanographic transition zone.

The marine zone shares the tropical dry climate of the Nayarit Pacific coast. Sea surface temperatures range from 22°C in the coolest months to 30°C during El Nino events. The rainy season from June to October brings warmer water, increased moisture, and occasional tropical storms. The dry season from November to May corresponds to the period of highest marine productivity driven by coastal upwelling. Strong northwest winds drive upwelling along the Nayarit coast in spring, bringing cold, nutrient-rich water to the surface and triggering plankton blooms. Visibility in the marine zone is best during the dry season with 20 to 30 meters underwater clarity.

The waters around Isla Isabel were fished by indigenous communities from the Nayarit coast for centuries, particularly for shark, tuna, and sea turtles. Commercial fishing for sharks and sea turtles intensified in the mid-20th century, significantly reducing populations before the island received protection. Sport fishing vessels from San Blas began targeting large pelagic fish in the 1970s. Diving and snorkeling tourism attracted by the island's renowned sea lion encounters began in the 1990s and has since become the primary human use of the marine zone. The island's scientific research program run by UNAM has monitored marine ecosystems since the 1970s.

The Zona Marina de la Isla Isabel was established as a national park to complement the existing Isla Isabel National Park with formal marine protection. The marine zone designation provides legal authority to regulate fishing, diving, and navigation within the surrounding waters. CONANP manages both the island and marine zone as an integrated unit, with ranger patrols covering both the land and sea. The marine zone is coordinated with the broader CONANP Pacific marine protected area network, including cooperation with the Islas Marias Biosphere Reserve to the northwest.

Snorkeling and scuba diving in the marine zone are the primary activities, with sea lion encounters the signature experience—sea lions approach divers with playful curiosity, circling and somersaulting. Reef diving reveals Pocillopora corals, parrotfish, and moray eels. Blue-footed booby feeding behavior is visible from the water surface as birds plunge at high speed into the sea. Whale shark snorkeling is offered by San Blas operators when sharks are present. Kayaking around the island perimeter explores the rocky coastline and sea caves. UNAM research station activities occasionally include citizen science involvement.

Access is from San Blas, Nayarit, by chartered panga or larger vessels, a journey of 2.5 to 3 hours depending on sea conditions. No regular ferry operates. The marine zone has no on-water facilities. Landing on the island requires both island and marine zone permits from CONANP. Visitor numbers are limited to protect nesting seabirds. San Blas town offers simple hotels, restaurants, and boat charter services. The dry season from January to May is best for calm seas and clear water. Equipment must be brought from San Blas.

The marine zone protects the productive ocean environment that sustains Isla Isabel's extraordinary wildlife populations. The primary threats are illegal fishing within the protected area and potential oil and chemical spills from vessels transiting the commercial shipping lane between Manzanillo and Mazatlan. CONANP patrols enforce fishing prohibitions and regulate dive operator behavior. Sea turtle nest protection on the island beach is coordinated with marine monitoring of turtle movement in surrounding waters. Microplastic pollution accumulating near the island is an emerging concern. Scientific monitoring of seabird breeding success links marine fish availability with ecosystem health indicators.