Map of ACG showing marine ecosystem in blue band off coast

First established as the 23,000-hectare marine portion of the new Parque Nacional Santa Rosa in 1971, the ACG marine ecosystem was initially ignored, other than hoped-for protection of spectacular numbers of Ridley’s nesting sea turtles (mostly Playa Nancite) and prohibition of mass commercial fishing or fishing with explosives. Then, in 1987, the marine national park protection status was extended to the northwest along the coast as a six-kilometer wide area of an additional 20,000 hectares, to generate today’s 43,000-hectare Sector Marino, which includes the small islands off the west side of Peninsula Santa Elena.

Small beach called Nancite with female turtles crawling up from the sea so dense you could walk across the beach on turtle backs

An arribada (mass nesting) of female Ridley turtles on Playa Nancite, Santa Rosa (photo: Steve Cornelius)

While Sector Marino has long been a site of artisanal fishing, which intensified during the Sandinista-Somoza war that drove fishermen south from Nicaragua, the long distance from Cuajiniquil and somewhat treacherous seasonal heavy winds largely protected it from intense biodiversity devastation. Once the political turmoil of the expropriation of Sector Santa Elena was completed in 2000, the long and still ongoing process of weaning the artisanal fishing out of the dying coastal fishing industry from its direct marine carnivory in Sector Marino began as an act of marine ecosystem restoration akin to the ongoing and highly successful terrestrial ecosystem restoration that had begun 30 years previously with the declaration of Parque Nacional Santa Rosa, and intensified from 1985 on with the germination of ACG. Sector Marino is to be a 100% no-take Sector of ACG, though it is expected that there will be steady harvest from fish leaving the site.

Freshly caught hammerhead shark on small fishing boat with Osvaldo Espinoza (now a parataxonomist), 1980's

Hammerhead shark on small fishing boat with Osvaldo Espinoza (now a parataxonomist), 1980's (photo courtesy O. Espinoza)

Children in lifejackets on boat studying fish identification guide

Children in Marine Bioawareness program studying sealife identification guides (photo: MM Chavarria)

While the islands in Sector Marino were almost cleaned of their biodiversity by fires set by camping fish killers, introduced Norway rats (Rattus norvegicus), and at least four centuries of logging (and probably millennia of indigenous hunting and harvest), the underwater biodiversity is still extremely diverse and now recovering. The high contemporary biodiversity is based on reduced artisanal fishing in these distant and wind-prone waters, and second, on the upwelling of deep-ocean mineral-rich waters bathing the geologically diverse rock cliffs, sand and pebble beaches. The major mangrove swamps in Bahia Potrero Grande, fed by the seasonal Rio Potrero Grande and the rainy season runoff from many small streams carrying forest litter, also adds to the diversity of habitat types, and hence species, within this ecosystem.

Man with small net in river fishing for specimens of new species of fish

Small river upstream from mangroves; A. Masis searching for specimens of a new fish species

Looking down from hilltop at a building below on island just off the coast

Field station on Isla San Jose, headquarters for the Islas Murcielago

Quick-visit short-term biodiversity surveys of fish, invertebrate and coral species in Sector Marino show clearly that it is among the most species-rich and habitat-rich areas of the Costa Rican Pacific mainland coast, but no thorough year round and multi-year biodiversity inventory has been conducted. When it is, it will show many surprises of both new species and species thought to occur only elsewhere. It will also begin to open the door to detailed ecotourism and understanding of the insidious marine contamination becoming every day more abundant on Costa Rica’s Pacific coast, but relatively light in Sector Marino because the land side of this sector is not “developed” and will not be, and because of the idiosyncrasy of local currents. The beaches of Sector Santa Elena and the northern part of Sector Santa Rosa appear to be among the only intact sand and pebble beaches on the Costa Rican Pacific coast.

Ray leaping out of the water in a small bay

A courting ray in a small bay on the Santa Elena Peninsula (photo: Luciano Capelli)

Group of rays leaping synchronously out of the water

Many very active courting rays together in a small bay on Santa Elena Peninsula (photo: Luciano Capelli)

It seems to be generally unappreciated that marine biodiversity is a great deal more than red snapper in the market and pictures of pretty aquarium decorations. It has easily a rich a natural history as the adjacent mainland, but the marine world has been constantly examined through the lens of edibility, with some so-called “sport” killing added in. While every one “knows” what a coral reef “looks” like, humanity is just about as ignorant of marine biodiversity as it is of deep rain forest.

2 children underwater with masks and snorkels fascinated by a live orange seahorse

Children meeting their first seahorse on a snorkeling trip of the Marine Bioawareness program (photo: MM Chavarria)

Large humpback whale dead on beach being experienced by a teacher and school children

Teacher and children of the ACG Biological Education Program (PEB) looking closely at a beached dead whale, Santa Elena Peninsula 2000 (photo: PEB)

Powerful lower jaw of a dead fish showing grinding molars

This lower jaw from a fish was clearly powerful and equipped with molars for grinding their food.  Found on Playa Junquillal 27 July 2002

Many small marine fish in shallow water

Small marine fish in shallow water (photo: LF Chavarria)

Dead fish on beach at tideline

Large fish washed onto beach

Mangrove swamp, many trees with stilt roots

Mangroves swamp at Potrero Grande, Santa Elena Peninsula (July 2001)

Mangroves behind the beach on Santa Elena Peninsula, river mouth

Mangroves seen from the air, Playa Potrero Grande, Santa Elena Peninsula (June 2007)