grit engineers flail
This final installment of the parrotfish series is about sand castles.
To understand the parrotfish-sand castle connection we must consider what a parrotfish eats. Parrotfish are herbivores and eat algae. But the algae is attached to coral, so parrotfish eat coral for the algae. Nutrients are absorbed from the algae but what is a fish to do with all that calcium carbonate filling its digestive tract? Poop it out as sand of course! And poop they do. Parrotfish poop so much that Hawaii’s beaches are thought to be primarily comprised of parrotfish poop. The island of Vakkaru in the Maldives is a giant 0.19 km2 mound of parrotfish poop. The parrotfish’s ferocious coral consumption and delightful defecation affords it a theme song and status as a bioeroder.
So what happens when there aren’t parrotfish in the water building sand castles?
Well first, coral reefs are suffocated by algae. Thereafter, the reefs will be devoid of fishes. Mangy and fishless reefs don’t exactly boost tourism, support sustainable fisheries, or maintain ecosystem health.
This scenario is the reality for many coral reefs in the Caribbean. Why have the parrotfish disappeared? Overfishing is the primary culprit according to an extensive and collaborative study utilizing over 40 years of data. What needs to be done? The International Coral Reef Initiative put forth recommendations to repair the reefs. The priority, while keeping an open dialogue with all stakeholders (e.g., indigenous communities, industry, etc.), is to implement fisheries regulations that will aid in the recovery of parrotfish populations. Not an easy task, but one worth tackling to protect valuable natural resources.