Reef and the Parrotfish: Key Players in the Health of the Marine Ecosystem



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TBC

To most people, the word “reef” probably conjures up images of a coral reef in clear, warm water, densely packed with a huge variety of corals in rainbow colors, and teeming with fish-life. Indeed, that’s how a healthy coral reef should look. Coral reefs occupy less than 1% of the earth’s surface but contain an astonishing 25% of all species worldwide. Their global reach is so limited because the reef-building coral species cannot tolerate sea temperatures below 64°F / 18° C, and can only thrive between 73° and 84°F / 23° – 29° C.

Due to cold upwelling currents during the winter months here in the Gulf of California, we don’t have reefs made of coral, because most reef-building corals cannot survive our low winter sea temperatures. The reef at Cabo Pulmo is an exception, being an ancient coral reef with an estimated age of 20,000 years. But we do however, have extensive rocky reefs – a more widely spread type of marine topography worldwide than the coral reef, consisting of mainly volcanic rock formations and boulders from land erosion.

In general, rocky reefs are not as rich in species diversity as coral reefs – even here at the Tropic of Cancer – but are just as important to their marine eco-system because they are the major feeding ground for most marine life forms, from the smallest fish to the large pelagics such as sharks, dolphins and sea lions. A healthy, rocky reef can attract great numbers of fish and marine mammals and can support the growth of the more hardy coral species that need less sunlight, like sea fans, thorny corals and cup corals. Even some reef-building coral species can proliferate in the sunny shallows.

 

So what makes a healthy rocky reef? The bottom of the food chain starts with the drifting planktonic life forms that feed the very largest animals –whales, whale sharks, manta rays, etc. in open water – or that may settle on the rocks and form a rich and varied carpet of encrusting and sessile organisms – including algae, sponges, tunicates, tube worms, mollusks and some coral species – on which smaller fish and invertebrates feed. These in turn feed bigger fish further up the food chain. A healthy rocky reef is therefore one with a great diversity of lower life forms that inhabit its rock surfaces.

This is where the reef grazers play their important part – and none more so than the Parrotfish! This iconic caretaker of the reef owes its name to its parrot-like beak as well as to its vivid colors that vary between the male, female and juvenile forms of the same Parrotfish species. It inhabits in abundance both coral reefs and rocky reefs in tropical waters around the globe. There are about eighty identified species in the world, in sizes ranging from thirty to one hundred and twenty centimeters in length.

Here, in the Archipelago Espiritu Santo National Park and the La Paz area, only four different species of Parrotfish have been identified. They graze predominantly on the algae that grow on the rocks and on the hard corals. But unlike the purely herbivorous grazing fish, such as the Surgeonfish, Parrotfish also eat mollusks, echinoderms and hard corals. Their grazing activity prevents the overgrowth of algae that rapidly invade the rock surfaces and smother corals, thereby preventing a greater diversity of organisms in the food chain from settling and thriving.

In the Gulf of California, therefore, the vital role of the Parrotfish is as a cultivator of coral colonies and of diversity in the rocky reef environment. Furthermore, due to its mixed diet that includes corals and shells, it grinds down and ingests the calcareous structures of these organisms and defecates a great quantity of calcium carbonate throughout its lifetime. In this way the Parrotfish performs another essential service to the reef, by scattering calcium carbonate all over the rocks and shallow seabed, where it acts as a mortar, to fix the sandy substrate and facilitate the settlement and growth of corals. Over eons some of that white sand makes its way onto the beaches of the islands and shores of the Gulf of California, and gives us those glorious, soft white sand beaches that we all enjoy so much!

Espíritu Santo Es Parte De Ti is a local, grassroots campaign that aims to involve the La Paz community in the recovery of the depleted reefs and reef fish populations in Espíritu Santo National Park, by generating community pride in this outstanding natural resource and by advocating responsible fish consumption. We are encouraging people to avoid consuming species that are critical to the health of the reef ecosystem, particularly the Parrotfish, which is a popular food species whose numbers have been hugely depleted through illegal fishing methods.

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