Influencing Legislation to Benefit Mangrove Crabs & Livelihoods in Brazil
The climate and biodiversity crises require global action to protect habitats and species. Our Edinburgh Napier Centre for Conservation and Restoration Science is an interdisciplinary research centre committed to delivering innovative science and solutions to help conserve, rebuild and enhance biodiversity across terrestrial, freshwater and marine ecosystems.
Problem:
Mangrove crabs are revered in Brazil and the main revenue for many low-income fishers. To protect the species from being over harvested during mass-mating events, the Brazilian government regulates fishing, however there was a mismatch between capture bans and the actual occurrence of mating, which sparked conflict and law incompliance between government and local fishers.
Solution:
Edinburgh Napier co-founded the researcher network, REMAR, a collaboration with nine Brazilian universities and research institutes. The aim of REMAR was to identify the drivers of the breeding pattern of a mangrove crab to help conserve the species and improve its fisheries management, while also securing dependant livelihoods in Brazil.
Dr Anders Jensen Schmidt, Universidade Federal do Sul da Bahia, Brazil & Professor Karen Diele, Centre for Conservation and Restoration, Edinburgh Napier University.
Improving science-informed crab fisheries management in Brazil
The mangrove crab, Ucides cordatus, is a national delicacy in Brazil, and ecologically and economically important, providing food and livelihoods for over 10,000 low-income fishers and their families along the coast.
To protect the crabs from being over harvested, fishing has been regulated by the Brazilian government, however regulators had lost credibility among fishers, due to a mismatch between precautionary capture bans implemented to protect the crabs during their conspicuous mass-mating events, and the actual occurrence of the mating.
To investigate the reproductive rhythm of the crabs and to improve their fisheries management, a researcher from Edinburgh Napier’s Centre for Conservation and Restoration Science partnered with a Brazilian colleague from the Universidade Federal do Sul da Bahia to form the REMAR researcher network.
Citizen science app to support public engagement & sustainable fisheries
In addition to REMAR’s monitoring of the crabs’ mating inside the Brazilian mangroves, the researchers also teamed up with computer scientists and undergraduate students from Edinburgh Napier, who helped develop a citizen science app, REMAR Citizen. Since the app was launched in 2017, it has been downloaded more than 1,000 times by fishers, merchants, students and tourists in 16 states across Brazil, with users reporting when they spotted a mating event and what the moon phase was.
REMAR identified a fascinating pattern of the crabs’ reproductive behaviour, detecting that mating occurs when the tidal amplitude is largest, which varies between new and full moon, within and between years, and that the crabs can anticipate which springtides will be largest.
Based on the discovery of the linkage of the mating with two geophysical cycles, REMAR developed an algorithm considering moon data, tidal charts, and the crabs’ anticipatory behaviour to predict when they will mate in any future month or year.
This algorithm, now used as a forecasting tool by the Brazilian government, has improved the placement of the capture bans during the crabs’ breeding season. This new science-informed legislation is delivering significant benefits for the livelihoods of fishers in 12 federal states, halving the costs of policing capture bans, and helping to ensure that the crabs in Brazil’s mangrove are fished sustainably.