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Ecology

Life in the mud

The mangrove swamp crab and its traditional hunter depend on each other for survival

ANDRÉ ALVESAmong the rhizophores the crab hunters circulateANDRÉ ALVES

To move through a mangrove swamp is not for everyone. You can be stuck in the mud up to your knees and lose your shoes on your first step, if they are not well tied. Without mentioning the strong smell and the tiny sand flies that quickly cover any exposed skin. For each step it is necessary to raise one’s foot out of the mud, without tripping over roots – they are air bladders, which emerge from the mud vertically like snorkels from hundreds of divers and take air to the submerged roots, and rhizophores, supports that jut out of the trunk and leave the red mangrove (Rhizophora mangle) more like a web than a tree. On fixing one’s eye on this tangled mass, everything appears to be moving. Innumerable crabs of various species live buried in the mud, between the roots, on top of them or even in the trunks and tree tops. Some are frequently on the Brazilian menu, above all the mangrove crab [caranguejo-uçá] (Ucides cordatus). Also part of this ecosystem is the crab hunter. There are thousands of Brazilians who depend on the mangrove swamps for their livelihood, but they are even more invisible that the crabs for the rest of society (see Pesquisa FAPESP Nº 68). For Jaime Doxsey, from the Federal University of Espirito Santo (Ufes), the crabs should be recognized as part of a tourist complex as happens with the Espirito Santo pot makers, since the crab dish is one of the most famous plates of the local culinary.

Doxsey coordinates the Crab Project, which studied the ecology of the crabs and crabbers in six mangrove swamps in Greater Vitória, in the state of Espirito Santo. The project ended in 2005 and involved nine teams, which evaluated aspects such as the bio-ecology of the land crab, its commercialization, the socio-economical and cultural situation of the crab hunters and their health. And it did not just involve research: it included activities of environmental education for the riverside communities, proposed alterations in the hunting legislation and regulated the hunter’s profession. The researcher believes that the results show how it is possible to improve the lives of the hunters and at the same time protect the mangrove swamps.

Ideally, the crab hunter lives close to the swamp. In Mamanguape, an environmental protection area that houses one of the best preserved mangrove swamps of the state of Paraíba, this is the case. In Greater Vitória this is not the case, according to researcher Doxsey. With the urbanization of the mangrove swamp areas, the traditional fishermen have been displaced from where they used to live and thereafter people settled who had no activities related to the ecosystem. Even at that, the hunters spent a good part of their time in the mangrove swamp: in general four days hunting crabs, which they tie off, six by six. These strings come in pairs and form a bunch with a dozen crabs. On the following days, they sell their collection to marketeers, who distribute it and keep a good part of the profit.

In the mangrove swamps a large part of the life cycle of many marine animals occurs. These are calm waters, with lots of organic material and low salinity. To destroy them would have an immense economic impact, as it would eliminate crabs, small crabs, fish, shrimps and shellfish. Even at that, these mangroves are considered to be dirty and inhospitable and end up becoming rubbish dumps, shrimp farms or being land filled for condominiums by the sea.

Because of the loss of the ecosystem and pollution, as well as a mysterious illness and indiscriminate collecting, the stocks of the land crab are endangered all along the Brazilian coastline. In the estimation of Yara Schaeffer-Novelli, from the Oceanographic Institute of the University of São Paulo (IO-USP), a land crab takes nine years to develop from an egg to a commercial size. For this reason, the depleted populations take a considerable time to recover.

The Brazilian Institute for the Environment and Renewable Natural Resources (IBAMA) is establishing a defense period, which prohibits collection during the reproduction season and of land crabs with carapaces of less than 6 centimeters. But these protection measures are frequently inefficient. Rômulo Alves, from the State University of Paraíba, believes that the greater problem is to ignore the crabbers. “Their traditional knowledge is valuable for establishing conservation and management plans. Different studies have shown that the non-inclusion of traditional communities and their knowledge leads to inefficient management plans throughout the world”, he says.

The information gathered by the researchers from the crab hunters of the Mamanguape river estuary, 70 kilometers to the north of João Pessoa, the capital of Paraíba, has revealed knowledge about the influence of tides and the moon on the crab’s ecology that up until now had not been published in scientific literature. This knowledge is passed from one generation to another, therefore being the patrimony of the traditional crabbers. Opportunistic crab hunters, who enter the mangrove swamp when they need to complete their income or their food, are short of this knowledge and for this reason have less chance of having success in the capture and cause more damage to the ecosystem. Knowledge of the signs of shedding, for example, is important since at that moment the crab produces lots of calcium and for this reason is bitter. And shortly after the shedding they are thin and less tasty.

ANDRÉ ALVESThe land crab is essential for the functioning of the mangrove swamp and for the table of many BraziliansANDRÉ ALVES

Doxsey’s Crab Project showed how local information can have major impact. After having studied the ecology of the land crab, the group verified that in the state of Espírito Santo reproduction occurs between December and April. This is the “walking”, when the crabs leave their holes and walk through the swamp in search of partners. But the Capixaba “walking” did not correspond to the defense period determined by IBAMA, and this had to be corrected.

But protection of the crab is not enough. The social survey made by the group led by  Alves at the Mamanguape estuary showed that the traditional crabbers, those who have lived in the mangrove swamps for generations, are aware and agree with the need to impose limits on catches. Only in this way can they guarantee the maintenance of the resource upon which they depend. But if the hunting were prohibited during the reproduction months, the human inhabitants of the mangrove swamp would be without any alternative resource.

This was one of the great conquests of the Crab Project, which instructed the hunters as to their rights by way of talks in the communities and the distribution of booklets on Fisherman Citizenship. The researchers worked with the local IBAMA, the Social Welfare and the Health Service to turn the crabber into a citizen. Before the project, the inscription portfolio for professional fisherman did not include the sub-category of “crab hunter”, in such a way that the activity did not officially exist. Now the communities of the crab hunters of Greater Vitória have the right to unemployment benefit during the defense period.

The measure allows the traditional hunters to protect their natural resource. But as yet the problem of disordered collection, carried out in the main by opportunist hunters who do not know the crab’s ecology and use more destructive techniques in their collecting, is still not resolved. Alves suggests that it would be necessary to paralyze the activity during the reproduction period, involving the traditional hunters in the supervision  process.

Another important step was to instruct the local health professionals as to the recurring ailments in this profession. A survey made by the project’s team showed that many hunters have back pains as a result of the heavy bags that they carry. As well as this, cuts, scratches and dermatitis are common for this activity because of the roots and pincers of the crabs, aggravated by diesel oil with which the hunters smear themselves to escape the insects.

The researchers verified that in spite of the sale of 2,000 tons per year in Espírito Santo  the land crab stocks continue stable, with the exception of the Vitória Bay mangrove swamps where there are fewer males than one would hope for and the crabs are in a general manner smaller. This happens because campaigns underline the greater impact of females in reproduction, and for this reason the hunters favor the collection of males. “People don’t buy strings that contain many females”, explains Doxsey. Even so, with fewer males in the mangrove swamps the number of females on the strings has grown.

Part of the impact comes from the collecting method: manually, using a hook or a small net. The traditional hunters dominate all three techniques, which they use depending upon the conditions. But manually is taken as the traditional method whose proficiency defines the true hunter, who sticks his arm into the gallery build by the crab until he reaches its inhabitant. The technique has its accidents, but the hunters pride themselves in it exhibiting the combat scars on their hands. The hunt is selective, since the professional chooses the target by the crab hole characteristics. The male land crab has hairy claws that leave a trail at the entrance and allows the crabbers to choose the gender of his prey. As the diameter of the gallery corresponds to that of its inhabitant, the hunters do not lose time searching for animals smaller than that permitted.

In an article published in 2005 in the Journal of Ethnobiology and Ethnomedicine, Alves reports that he accompanied Mamanguape estuary crabbers and compared the expectation to the capture, and saw that in fact the specialists of the mangrove swarm have a high rate of success. It is for this reason that this technique causes less impact on the crab population and is also the one that least affects the environment. In terms of productivity, however, the manual method renders less than the other techniques (46.3% efficiency) – and success varies according to the experience of the professional. As they have to compete for the resource, very often the traditional hunters are obliged to use more productive methods.

The hooks are made in wood and their use depends on dexterity, but this was the most productive technique for the crabbers accompanied during the Crab Project (63.8%). The major drawback is that the animal suffers great pressure on its carapace and for this reason survives less after capture. This mortality reduces the commercial success, since the animals have to arrive alive at their selling point. For this reason many middlemen  reject crabs captured with the hook.

The small net is the form of capture most used by the non-professionals, although prohibited by IBAMA. They are nylon threads removed from potato sacks, fixed onto branches or rhizophores stuck into the mud close to the entrance to the crab hole. A source of impact upon the vegetation is exactly the breaking of the mangrove roots at the moment of fixing the net. But the more serious damage comes from forgotten nets, common when the hunter is sporadic and does not know the forest swamp well. The abandoned nets pollute the mangrove and cause the indiscriminate death of any animal that happens to tangle itself in them. Yara, from the IO-USP, related that these small nets very often end up in the estuary, where they can be eaten by turtles or birds and thus they are harmful even outside of the mangrove swamp.

Excessive collecting is one of the threats to the land crab on the coast of Brazil. But more and more the illness known as lethargic crab, which has decimated entire populations, is being highlighted. Many specialists believe that one is dealing with a fungus; there are those who say that agro-chemicals coming from sugarcane plantations cause this mortality. “There are lots of rumors in the name of science”, explains Doxsey. Yara confirms that what causes the illness is not yet proven. But for her the most plausible theory is that one is dealing with a virus that infects shrimp farms. “The hepatopancreas of the moribund or dead crab is the same as that of the infected shrimps”, she explains. She believes that the fungus is a secondary infection, which attacks the already debilitated crabs.

The biologist Renato de Almeida, from the Salesiana College of Vitoria, argues that the illness established itself in Brazil, at the same time that the shrimp farms were installed in the Brazilian Northeast on a large scale. When he was in the state of Bahia as part of the Rondon Project – Operation Northeast 2007, Doxsey observed that the illness already affected the region and the fishermen were capturing smaller animals. But it did not remain in the Northeast. “We have reason to believe”, alerts Almeida, “that the fungus has been transported by the coastal marine currents, predominantly in the north to south direction”. And has already arrived in the north of Espirito Santo State.

At the town of Ituberá, in Bahia, Doxsey coordinated a “Mini Crab Project”. It was well received and he believes that the seed of the benefits that the project has obtained in Espirito Santo was planted in Bahia. His work, as well as that of Alves’ group, shows how preservation efforts have to contemplate, include and listen to the communities that make up the ecosystem. “The professional crab hunter is the best guarantee for sustainability”, sums up Doxsey.

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