Recovery of Mouthless Crab (Cardisoma crassum) Populations in Mangrove Forests of the Chone River Estuary (Ecuador)



  • Foundation for Research and Social Development (FIDES)


  • 28/08/2014

  • REGION :

  • South America


  • Ecuador


  • Mangroves are considered one of the world's most productive ecosystems (RAMSAR Convention). In addition to their significant ecological role, mangrove habitats fulfill important economic, cultural, and social functions for the various communities settled on the banks of estuaries. Despite the environmental, social, economic and cultural importance, and the existence of a legal framework for protection, more than 80% of the mangroves in Chone River Estuary have been destroyed by the shrimp industry. This destruction has caused deteriorated living conditions in families that have lived off of the ecosystem for generations, mainly due to the decline and loss of species that have been part of local community’s food security. The FIDES Foundation’s intervention with families dedicated to fishing and gathering allows the generation of alternative livelihoods for mangrove communities of Manabí through the protection and sustainable use of mangrove resources. An important example of this is the recovery of the Mouthless crab in situ, in a process that combines ancestral knowledge and practices with new technical knowledge. The case study shows an ongoing pilot project that is generating positive results for the recovery of the mouthless crab.


  • Mangrove ecosystem, Mouthless crab, Local community, Livelihood


  • Maria Dolores Vera Economist, Masters in Agricultural Economics and Rural Development Mrs. Vera comes from a local rural community in Ecuador (South America) and works at the Foundation for Research and Social Development (FIDES). Her experience includes working with local rural communities in strengthening community organizations and economic activities, protected areas management, and mangrove ecosystem restoration. (Email: Gina Napa: As a women leader to the Ecuadorian people living in mangrove communities, Mrs. Napa works in community tourism, and promotes organizational strengthening and mangrove restoration activities in communities. At present, she is President of the National Coordinating Corporation for the Defense of Mangrove Ecosystems, which is a network comprised of 100 organizations of artisanal fishermen, gatherers and members of the Council of the International Mangrove Network.


1.1 Mangrove ecosystems and their importance.

Mangroves are found within the intertidal fringes of tropical and subtropical coasts, as this is a transitional ecosystem between marine and coastal environments. These areas consist of mangrove forests, marshes, estuaries, canals, lagoons, beaches and islands, whose ecological interactions constitute a number of abiotic and biotic components throughout the ecosystem.

Mangrove ecosystems are considered one of the world’s five most productive ecosystems by the RAMSAR Convention. They provide a number of ecologically important functions, which are important for the ecosystem’s equilibrium, such as:

  • Flood control: A strong, above ground root system stabilizes the shoreline by reducing erosion by providing protection from waves and tides
  • Protective barrier coasts: A dense and tall canopy acts as a barrier, which protects against storms and hurricanes
  • Filtration: Mangroves capture sediments and toxic substances contributing to water filtration before entering the ocean from the rivers
  • Desalination: Reduce the salinity of water entering mainland
  • Source of organic matter: Produce leaf litter and export biomass
  • Stabilizes microclimates: Produce oxygen and capture a high quantity of carbon dioxide from the air
  • Reproductive zone: Approximately 70% of the marine organisms spend some part of their life cycle in an area containing ​​mangroves or in coastal lagoons.

Photo 1: A woman gathering mangrove clams.

Photo 2: Fishing in the estuary.

In addition to their ecological role, mangrove forests fulfill many economic, cultural and social functions.  Several communities are situated on the banks of mangroves, and these people engage in activities dependent on mangroves, such as fishing and gathering shellfish.  Also, mangroves have been ancestral sources of food supply, used for charcoal and salt extraction, timber and firewood, tannins, medicinal herbs, and recreational activities including tourism.

1.2 Location of the Mangrove Ecosystem in the Chone River Estuary

The River Chone estuary is located in the province of Manabi, Ecuador.

1.3 Destruction of the mangrove ecosystem in the Chone River Estuary.

Despite the environmental, social, economic and cultural importance, and the existence of a legal framework for protection, more than 80% of mangroves in the Chone River Estuary have been destroyed by the shrimp industry.

According to the Center for Integrated Natural Resources by Remote Sensing (CLIRSEN)[1] quoted by C-CONDEM (2007), in 1969 there were 4,171.20 hectares of mangrove forest and by 1999 there was only 704.90 hectares, meaning a loss of greater than 80% of mangrove forests replaced by shrimp ponds constructed by fisherman. By 2006, there was a slight recovery of mangrove forests, from local communities’ efforts to protect the ecosystem.

Source: National Coordinating Corporation for the Defense of Mangrove Ecosystems (C-CONDEM)

1.4 Impact on local communities

The destruction of the mangrove forests in the Chone River Estuary, due to pollution and change in land use (mangrove forest and salt ponds for the installation of shrimp industry), has caused deteriorated living conditions for families whom have lived off of the ecosystem for many generations. The main problems faced by these families are:

–          Decreased fishing catch: The result of a day’s work in fishing and gathering shellfish has decreased by 90%, affecting food security in families.  For example, before the shrimp industry took over, on average 800 shell (Anadara similis and Anadara turberculosa) were collected per day, which currently less than 50 shells are collected per day.  Similar situations exist with other species, such as crabs, in estuarine fisheries.

–          Disease: The contamination of estuarine waters generated throughout the watershed (garbage, sewage, agrochemicals from agriculture, livestock and chemicals from the shrimp industry), has intensified the presence of diseases affecting communities doing their artisanal fishing and gathering practices in the estuary.

–          Loss of freedom of passage through public spaces: In Ecuador, mangroves, estuaries, rivers and beaches are national assets for public use, and the law decrees free passage in these areas. Within the mangroves, there are transit easements and paths that have been traveled ancestrally. Currently, the shrimp industry prevents fishermen from entering due to the placement of armed guards, dogs and electric wire, which affects the right to free movement in public spaces, when in reality community livelihoods depend on this territory.


The Foundation for Research and Social Development (FIDES) works with families who fish and gather for a living, in the generation of alternative livelihoods for mangrove communities of Manabí through the protection and sustainable use of mangrove resources. Their main activities include:

–       Mangrove ecosystem restoration: Due to the degradation of the mangrove ecosystem within the estuary, and continued shrimp industry activities which occupy almost the entire area that was historically mangroves and salt ponds, it is difficult to conduct a thorough restoration process; However, the FIDES Foundation and local communities implement restoration processes in certain areas through red mangrove reforestation (Rhizophora mangle), and recovery of mangrove species such as shell (Anadara similis and Anadara tuberculosa) and mouthless crab (Cardisoma crassum).

–       Community Tourism: As mangrove destruction has caused a decrease or extinction of a number of important species, including fish, clam, and crabs, that are an important source of food and income for local communities, community tourism creates an alternative activity that generates income for these communities, and allows these communities to maintain their connection with mangroves. As a major alternative for economic, community tourism plays both a social and environmental role, as it provides an income to families and avoids pressure on the reduced resources found within the ecosystem.

–       Strengthening Community Organizations and Policy FIDES works in local capacity building to increase the active community participation in protected area management, as part of the Chone River estuary became a protected area in 2004, as well as in the preparation and presentation of proposals for laws and public policies in favor of mangrove restoration and to protect the rights of the communities linked to this ecosystem.

–       Education with Youth and Children: FIDES works with schools in the assessment and recovery of ancestral knowledge of mangrove people, through training workshops in schools and colleges, and related events, such as drawing competitions, speech contests, murals, among other activities.


Within the activities for ecological restoration of mangrove ecosystems falls the recovery of the mouthless crab (Cardisoma crassum), an important species that serves as food for families and forms part of commercial activities in community tourism.

3.1 The mouthless crab and its ecological and socioeconomic importance.

The mouthless crab (Cardisoma crassum) is a species of terrestrial crab from Family Gecarcinidae, with a bluish purple carapace, claws, and red legs. It lives in tropical forests along the Pacific Ocean, from Baja California to Peru.

Photo 3: Mouthless Crabs

Unlike others, the mouthless crab is not able to stay submerged in water for long periods of time. It is terrestrial and live in J-shaped burrows which are one or two meters deep, built in drier soils within mangrove forests and in transition areas of humid or dry forests, as long as there is a brackish water source nearby.

In addition to serving as food for other animals, the mouthless crab helps conserve the mangrove ecosystem, as it accelerates the decomposition of organic matter during feeding. It works as a catalyst and regenerator of wetland plant communities, especially in mangrove and tropical humid ecosystems.

Even so, similar to other species in mangrove forests, the survival of the mouthless crab is negatively affected by mangrove destruction and overexploitation. The capture or harvest of the mouthless crab is an open-access artisanal activity, which generates income and serves as a food source for people in fishing communities that share these mangrove areas.

In the Chone River estuary, the mouthless crab population has declined drastically in recent decades, mainly due to the mangrove deforestation by the shrimp farming industry, which has also led to the disappearance of a number of species in the estuary. For this reason, community organizations in the Chone River estuary have worked towards the conservation, management and sustainable commercialization of the mouthless crab, and to carry out activities to increase local species populations in situ.

3.2 Current Legislation for the protection of the mouthless crab in Ecuador.

The mouthless crab is protected by a closed season twice a year, during which the capture and consumption of this species is prohibited. (Ministerial Agreement 016, published in the Official Gazette 284 from March 3, 2004).

–       Closed Season for Reproduction: January 15 to February 15

–       Closed Season for Molting: August 15 to September 15: Occurs during the crab growth period, when these crabs molt their carapace for a larger one.

As additional measures, it is prohibited to catch crabs with sizes smaller than 7.5 cm in carapace length, and the capture of females is prohibited. (Ministerial Agreement 004 of January 13, 2014)

3.3 Process increasing mouthless crab populations in situ.

Starting in 2012, efforts to increase mouthless crab populations were started by community organizations in the Chone River estuary, the process comprising of the following:

a)      Site Diagnostic.

An initial assessment is made to determine if the site meets the basic conditions needed for normal crab development and to establish a baseline of the quantity and condition of existing crab populations in site.

The basic conditions necessary include that the site is located near a body of water and has plants used for food by crabs, such as romero (Sesuvium portulacastrum), straw (Cyperus rotundus), ranconcha (Acrostichum aureum) and others.

Then, the baseline is established using indirect methods, by which the number and status of burrows are verified to indirectly estimate the density, structure and biomass of the population. Sampling is done using a 10 square grid measuring 25 m² each (the number of grids depends on the size of the site to repopulate), selecting several quadrants randomly and taking note of the number, size and state of the burrows (covered or open), and mud texture (fresh or dried). The disadvantage of this indirect method is that you cannot identify the sex ratio of crabs.

Photo 4: Part of a quadrant used for indirect sampling in Community Portovelo.

b)      Mouthless crab Reintroduction.

In order to reintroduce new individuals to an existing population, crab individuals are captured in estuaries with similar conditions to the estuary where the reintroduction is to be done. Crabs must be maintained in a corral for at least 3 days and fed so as to complete a process of internal cleansing.

The crab reintroduction considers a ratio of 75% females and 25% males, with crabs measuring 50 mm in their carapace width in order to achieve an early reproduction.

Photo 5. Measuring carapace width

Photo 6. Measuring carapace length

Before reintroducing crabs in any given site, crab characteristics are recorded for each individual: weight, measurements of width and length, carapace color and sex.

Photo 7: Data registration before repopulate of crabs.

Before reintroducing crabs in their new site, temporary artificial burrows are created with a one meter depth so that the crabs can use them until they are able to make their own burrows or choose to stay in the artificial one.

Photo 8: Making artificial burrows artificiales

Photo 9: Crab entering an artificial burrow

c)      Monitoreo del cangrejo.

The first monitoring is performed three days after repopulation, one monitoring in the second month after the repopulation, and then monitoring every three months thereafter.

First monitoring: A direct monitoring is performed on site, collecting all the dead crabs found at the site, to identify the percentage of deaths by sex.\

Photo 10: Dead crab found three days after repopulation.

Second monitoring: One month after repopulation, the second monitoring is performed by the indirect method with the same procedure as was used to collect baseline data.  The goal is to see an increase in the number of active burrows.

Periodic monitoring: Quarterly monitoring is performed using direct trapping methods, where wooden traps are placed the evening before the monitoring day.  The trap contains food bait to lure the crabs in. The total number of traps depends on the size of the site, and the traps are somewhat randomly placed, considering only the size of burrows and location of burrows.

Photo 11: Trap placed beside a burrow the evening before the monitoring day.

The next morning, the trapped crabs are checked and relevant information is recorded for each specimen (size, sex, carapace color, if female has eggs) and burrows (size, texture prints).

Photo 12: Crabs caught in the monitoring traps.

Photo 13: Measuring mouthless crab individuals trapped during monitoring.

Finally the crabs are returned to their burrows, after recording the respective data.

Photo 14: A boy returning the crab to its respective burrow.

3.4  Training

This process is accompanied by training and education of families that harvest the mouthless crab, and stresses the importance of sustainable management and enforcement of existing regulations.

3.5  Results.

The scientific information available on the mouthless crab is very limited. As a pilot project, these processes include the use of both ancestral knowledge from communities, and scientific knowledge from professionals.  There has not yet been an assessment of the results; however, quarterly monitoring suggests an increase in population density in the reintroduction sites and in other areas due to crab movement, or individuals seeking new breeding sites. The first results of this pilot project will be available December 2014, which will be shared when available.


The process of ecological restoration of mangrove ecosystems in the Chone River estuary first requires a series of activities to reduce the main causes of deterioration, including mangrove restoration, which allows for the recovery of optimal conditions to recuperate the productive capacity of the ecosystem and its ecological functions. These activities include:

–       Recovery of mangrove areas that were deforested illegally by the shrimp industry, which requires political will and decision making by the Ecuadorian government

–       Integrated management of the Chone River basin, which lowers pollution levels to the minimum, by relevant local governments.

It is unlikely that current policies and authorities are able to resolve all of the issues highlighted above in the short term; however, it is important to promptly initiate actions for ecosystem restoration.  It is particularly important to empower families who harvest crabs, especially in the reintroduction and monitoring of the mouthless crab.  Growing participation in these families allows for the following:

–          Recognition of important ancestral knowledge and skills that are incorporated into the recovery of the mouthless crab, and to establish dialogue about ancestral knowledge and technical knowledge related to the recovery efforts

–          Promote a sustainable recovery plan

–          Generation of income, achieved through the sustainable management of the mouthless crab and improving the living conditions of families who harvest crabs


C-CONDEM, 2007. Certificando la Destrucción: Análisis integral de la certificación orgánica a la acuacultura industrial del camarón en Ecuador. Quito, EC.

[1] The CLIRSEN was replaced by the Ecuadorian Spatial Institute, in July 2012 by Executive Decree 1246.