What are the options we have to transform booming export of wild-caught mud crabs from Sundarban into a sustainably managed fishery? We are exploring this challenge for quite some time now.
In October 2016, I’ve got the opportunity to discuss this with Dr. Chamniern Vorratnchaiphan when he was visiting Bangladesh to attend 13th Regional Steering Committee Meeting of the Mangroves for the Future. While sharing our views on different aspects of natural resource management, we also discussed the mud crab fishery of Bangladesh and Thailand. Mr. Chamniern hails from Thailand and currently, he leads the International Union for the Conservation of Nature’s (IUCN) country office there.
As Dr. Chamniern was explaining Thailand’s experience with the management of crab fisheries, the ‘Crab Bank’ came up. He explained how Crab Bank is changing the face of natural resource management in many South-east Asian countries, except for Bangladesh.
An Asian way of managing wild-caught mud crab fishery
It is still unclear exactly when and from where the idea was originated, but a recent review suggests that the earliest documentation dates back to 1980s in Japan. However, the idea got popular among resource managers in Thailand, Malaysia, Cambodia and Viet Nam during 2000s. Not just managers, the members of the fishers group from Chonburi Province of Thailand, and the central government and the Ministry of Agriculture, Forestry and Fisheries in Cambodia have also employed and promoted Crab Bank to manage their crab resource. While few operational details of ‘Crab Bank’ is flexible from region to region aligning the local socio-economic settings and perspectives, it is notable that the core theme of ‘Crab Bank’— saving gravid crabs and their newborns— remains largely different across practicing countries.
Evidence of four different models (i.e. Japanese model, Donation model, Purchase model & Loan model) of ‘Crab Bank’ has been reported so far from Japan, Thailand, Malaysia, Cambodia and Viet Nam respectively.
Japanese model follows the purchase of the gravid female crabs from fishermen by a cooperative, and then the release after marking the carapace so that fishers do not capture the marked one until they spawn or molt (female crabs generally molts after spawning). In Donation and Purchase model, gravid female crabs are donated to, and bought by ‘Crab Bank’, respectively; but neither does not follow the suit of marking the carapace before the release.
However, in the Loan model, fishers are incentivized with the access to loans if fishermen comply to release female gravid crabs and zoeae. In this model, fishermen are directly involved with the development of ‘Crab Bank’ and microfinance— unique in Cambodia. Interestingly, the incurred interest from the granted loan will be paid if the wild-caught gravid crab is released back in nature. While the basic tenets are similar, the operation, management, finance, monitoring, and governance vary in terms of socioeconomic and political setting in the above-mentioned countries and ecological reality of the different species in respective countries.
A model to adopt in case-specific bio-ecological contexts
The inclusion of ‘Crab Bank’ into fisheries management does not necessarily rule out the conventional management approach (i.e. ban-motivation-enforcement-punishment-compliance cycle), rather acts as an add-on. However, the approach deserved to be scrutinized from biological and ecological viewpoints. It is established that the wide range of species (e.g. Blue swimming crab, Red swimming crab, Mud crab, Grasped crab, Blood spotted crab, Sentinel crab, Rock crab, Swimming crab, etc) varies largely in terms of life history traits and ecological realities. Not only the peak breeding season, number of eggs per spawning, survival rate vary among different crab species, but also daily tidal waves, salinity level, and mangrove or coral association have varying roles in the life cycle of different crab species.
This circumstance—varying biological and ecological requirements for different crab species—demands a technically sophisticated and money crunching facility to spawn successfully with a minimum mortality or maximum survival rate. It has been widely reported that both blue swimming crab and mud crab are sensitive to climate change and changes in ocean chemistry, circulation, and precipitation.
The assessment of the ‘Crab Bank’ strategy, therefore, has to be case-specific, not generic. There are documented evidence of increased crab catch rates from Thailand, however, the increased catch rate is ambiguous to interpret whether the increased rate is the derivative of the abundance or the catch effort. The standard attribute of success should be Catch Unit Per Effort (CUPE) or total landing, not just catch rates as the term is skewed to false interpretation or misrepresentation. A study has also been found to refer that the increased number of crabs is based on fishers’ subjective report rather than conducting any scientific baseline survey. Besides, the disparity of information between fishers’ interview result (i.e. increased catch) and official records (i.e. decreased catch) reflects poorly on the recent assessment of ‘Crab Bank’ strategy. Nevertheless, it must be noted that assessment of the likely benefits of stocking crabs through ‘Crab Bank’ should be monitored in long-term, and not in short-run. Given the ecological preference and climatic sensitivity of different crab species, it is obvious that ‘Crab Bank’ is largely entitled to a ‘trial and error’ phase before we celebrate the idea disregarding the above-mentioned socio-ecological aspects and the assessment process.
While discussing with Dr. Chamniern, it crossed our mind that perhaps a trial and error attempt can be made by setting up a ‘Crab Bank’ in Bangladesh. However, even for an experimental purpose, it is important to consider the possible consequences of such effort as the collection of crabs adjacent to Sundarban region has its own set of overarching social, ecological and economic issues.
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