Most of the people of the Caeté Estuary in northeastern Brazil depend on the mangrove crab. Specifically, that’s Ucides cordatus, a species of crab that lives on the Atlantic coast of North America from Florida down to Uruguay. But sadly, that’s all Wikipedia says about it. The WoRMS database of marine species isn’t much better: it just says it’s also known as the swamp ghost crab. (Maybe that’s why we can’t find anything about it!) Luckily, even though there’s not much about Ucides out there, there are many different species of mangrove crabs, and they’ve got lots in common.
Mangrove and crab products are worth more money than some households make in a month.
The mangrove crab
Generally, these crabs live among and in mangrove forests. These are waterlogged coastal forests made up of mangrove trees, which are specially adapted to saltwater and tides. The crabs may even be a keystone species – in other words, incredibly important to the ecosystem – for these forests. That’s because they eat and process leaf litter, recycling it back to the forest floor; they’re food for young fish (helping mangroves support fisheries, like in the Sea of Cortez); and their burrows help to aerate the soil. And in Caeté , they do a lot more than that.
The Caeté Estuary, Brazil
First, we need to point out that the Caeté River is in the state of Pará, on the northeastern coast of Brazil, and is definitely not the Caeté that is near Belo Horizonte, which is very much landlocked. The Caeté River empties into the Caeté Bay and the Atlantic Ocean, and there are large and rich mangrove areas along the river, estuary, and coast.
Residents of the area are mostly rural, and they live subsistence lifestyles. Many people don’t or can’t work, due to low education levels, and they rely on natural resources for basic needs like food, fuel, and shelter. As you might expect, mangroves are central to their lives. They use mangrove wood for building materials, fish traps, and firewood; collect fish and shellfish; and forage for medicines. In cash, these would produce more money than some households make in a month! And this means that whether these products are sold or not, they help to alleviate poverty – for example, locals often collect snails and mollusks as a last resort to prevent hunger. And on the other end of the spectrum, some residents do sell or trade mangrove products.
Crabs are a keystone species for mangrove ecosystems, and for the people that rely on them.
But of all of these, the mangrove crab is by far the most important species. Almost half of all households collect and sell it, and for almost all of them, it’s the main income source. Some people even collect it for commercial processing and trading. Including subsistence and commercial activities, over half of the entire population depends on the crab for income. Pretty good for a crab we can’t even find!