From Mayumba National Park website:

Mayumba National Park protects an area of coastal sea of approximately 900 square kilometers, and a narrow 1km x 60km strip of beach and coastal vegetation. The Mayumba coastline is characterized by long exposed sandy beaches and extensive freshwater, tidal or brackish lagoons. The beaches support a rich shoreline fauna including monitor lizards, genet, mongoose, ghost crabs and shore birds. Buffalo, elephant and other forest animals are frequently found on the beaches and amid the dense dune vegetation that fringes the coast. Mandrill, gorilla, chimpanzee, and other primates inhabit the forest-savannah mosaic behind the dunes. The lagoons, some of which are extensive and extend for many miles inland, laced with islands, channels and rivers, are immensely productive systems supporting a wealth of fauna and flora, much of which takes advantage of major mangroves, flooded forests and swamplands. Hippo and crocodile are found here, as well as the rare and threatened West African manatee. Mangroves are critical developmental habitat for a wide range of coastal fish species and are important for many bird species.

Gabon hosts the single largest population of nesting leatherback turtles in the world each year between November and April. If Gabon is the world capital for nesting leatherback turtles, then the turtle capital of Gabon is Mayumba. Upwards of 550 females may come ashore in a single night in the 80 km from Mayumba town to the border with Congo; in places a density of over 20 females per kilometer. The protection of critically endangered leatherback turtles is one of the main reasons the Park was created.

In addition to its notable turtle population, Mayumba sees almost 10% of the world's humpback whales pass through or remain in its waters each year on their annual breeding migration; rare and little-studied humpback dolphins have been found close to the coast, sharks and rays appear to be abundant in the area, and bony fishes are also found in large numbers.

 

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More Information:

Illegal Industrial Fishing Threatens National Park and Local Livelihoods...Mayumba Fights Back (2009)

With respect to Mayumba National Park protecting turtles or valuable fish stocks, the obvious answer is that it is not working. (2009)

Mayumba, Gabon
from wikipedia: https://en.wikipedia.org/wiki/Mayumba,_Gabon

It is known for its long sandy  beach  where  leatherback turtles  nest. The most common ethnic groups are Vili, Lumbu, and Punu,and locals of Mayumba town call themselves 'Mayesiens'. It is home to an  airport , several small restaurants, and a  market . There are seven primary schools in the area, and one  junior high school  of about 500 students. Mayumba lies 20 kilometers (12 mi) north of  Mayumba National Park , the only national park in Gabon that is dedicated to the protection of marine species.