Could crabs provide a new source of sustainable protein?

Lessons from our Freshwater Crab Aquaculture project

The farmed crustacean market remains dominated by shrimp, with 5.7 million tonnes produced worldwide in 2024*, but crab meat is in increasing demand. Chinese mitten crabs (Eriocheir sinensis) and mud crabs (Scylla spp.) are favoured by growing numbers of consumers in China, East Africa, South East Asia and other Indo-Pacific countries. This has resulted in a growing, and lucrative trade in these crabs with 300,000 tonnes of mud crabs, and 800,000 tonnes of Chinese mitten crabs now produced annually*, but as these are estuarine-brackish species, their production is geographically limited or constrained by access to hatchery produced seed. By comparison, true freshwater crabs have a lifecycle that is completed entirely in freshwater, with females often brooding their young and are less constrained by these factors.

In many parts of the world, including India, freshwater crabs are caught from the wild as a subsistence resource or a cultural recreational activity. Recent research at the University of Plymouth, led by Dr Lucy Turner , has demonstrated both current and future demand for freshwater crabs (specifically the brown crab Barytelphusa cunicularis) from all sectors of the value chain, all the way from subsistence collectors to some of the best crab and seafood restaurants in South Asia. Conversely, at the same time the wild catch is known to be declining due to the impacts of over-harvesting, habitat loss, pollution, and climate change.

The challenge now is to capitalise on the fact that for many end-users freshwater crabs are a sought-after source of tasty protein and micronutrients, and to upscale their availability to different sectors by moving from an artisanal, wild-caught commodity, to aquaculture produced product.

Our research has explored some of the obstacles and opportunities surrounding moving to aquaculture production of freshwater crabs in India, the world’s most populous country, and a net food exporter, but which still faces challenges including malnutrition, and protein and micronutrient security, that are issues for many of its population.

Subsistence resource or cultural recreational activity?

Many freshwater crab catchers in India are from some of the poorest and most marginalised groups in society. Some of these spend up to five hours a day foraging for freshwater crabs, sometimes alongside hunting for other food items. Some of these catchers will benefit directly from their catch as a means of subsistence food source, whilst others will also spend time (often many additional hours per day) selling surplus crabs either directly to consumers, or to middle-men who will, in turn, sell the crabs on.

As per basic economic principles, the profit margin is known to increase at each trading stage. There is clear potential for an increase in incomes for those at the bottom of this value chain (the collectors themselves) if they could switch to producing a farmed product, ensuring a plentiful year-round supply.

At the same time, research has shown that large numbers of the growing urban middle class in South India have often spent their childhood – or still regularly visit relatives – in the countryside. As part of this, many recount fond experiences of catching, cooking, and eating freshwater crabs in a manner similar to summer berry foraging in North West Europe. As this sector of society continues to grow in India (more than 400 million Indians; approximately 30% of the population now make up this group), the increase in the recreational sector encompassing these types of activities has enormous potential, and could further drive future demand for freshwater crab catching as a cultural experience.

Is there demand for fresh and processed crab meat?

Crab meat is nutritious and tasty, and contains many micronutrients (including vitamins A, B12, C and E, and minerals zinc, iron, copper, phosphorus, potassium and calcium). Many South Indian consumers are aware of these properties and would like to be able to have greater access to this source of protein. Due to increasing supply problems at rural local-market level many consumers not only report the increasing scarcity of live freshwater crabs for sale, but also significant price increases in recent years.

At the same time, consumers also bemoan the lack of a dedicated, covered marketplace to act as a hygienic focal point for sale of freshwater crabs and other inland-produced food commodities. This may sound like an obvious piece of infrastructure that should be provided by local government or trade associations, but its lack highlights the relative poverty of some of the rural areas where these crabs are a notable protein source. If these facilities could be provided, this would potentially drive increased sales as consumers and producers would have a meeting point to complete their transactions.

If freshwater crabs could be farmed, and production upscaled then several products could be produced, not just live crabs, but potentially also a year-round processed vacuum-packed product. This could go some way towards addressing supply problems, and would also ensure distribution, not only in rural communities, but also from inland areas towards coastal regions. Restaurants reported demand for freshwater crabs, when available, but even those situated towards the coast whom currently serve mud and/or marine crabs suggested that if supply issues could be overcome they would be willing to add freshwater crabs to their menus as a regular item.

Dr Lucy Turner
Lecturer in Marine Biology

How can we culture freshwater crabs?

Over many years, basic research has been undertaken on the reproductive biology of B. cunicularis. We know that they complete their entire lifecycle in freshwater and are continuous breeders, that brood a relatively small number of eggs. This maternal investment is very different from the majority of their marine cousins, who are broodcast spawners. Even upon hatching they continue to brood their young until they are well developed into miniature ‘crablets.’

In addition, recent work has identified some physiological differences in the response to environmental variables between different populations of B. cunicularis across South India which will be important for optimising the siting of any potential future hatcheries. India has vast swathes of inland waterways, and the amount of area available for potential culture of freshwater crabs is huge. However, despite the long history of these crabs being used as a lab model, no specific scientific work has been undertaken exploring their potential for culture.

Working with academic partners in India , we have demonstrated the demand for freshwater crabs across the value chain, but basic aquaculture suitability studies now need to be conducted. We need to understand if culture will have any negative impacts on their reproduction – can they complete their entire lifecycle in captivity, and what can be done to optimise this, and growth?

The other two major unanswered questions pertain to feed: like all other aquaculture production, nutritious, sustainable feed with an efficient conversion ratio needs to be identified and produced, and the propensity and susceptibility to disease of these crabs needs to be quantified.

Once these questions are answered in first stage feasibility studies, we can move to the next stage of field trials, alongside an education programme for potential crab catchers whom are interested in aquaculture of these crabs – our previous work indicated a 100% interest rate amongst all those crab catchers surveyed. The focus will be on producing a small-scale, high-value, sustainable product but at a scale that has a lot to offer as a new, accessible aquaculture produced protein source.

If you would like to know more about our freshwater crab aquaculture research, or would like to discuss collaboration opportunities, please contact Dr Lucy Turner or visit the project webpage .

^{* As reported by the Food and Agriculture Organisation of the United Nations (FAO)}

This article is adapted from a piece published in International Aquafeed, June 2025, written by Dr Lucy Turner .

Sustainable Aquaculture and Fisheries

At Plymouth, a broad perspective on aquaculture and fisheries management is enabled by our transdisciplinary, systems-thinking approach embraces.

From the health and nutrition of farmed fish, crustaceans and bivalves, to marine conservation, fish tracking, habitats and natural capital, our research explores how all of these diverse elements help contribute towards responsible marine and freshwater food production, and, in doing so, how they support coastal economies and contribute to the national food security agenda.

Find out more about our Sustainable Aquaculture and Fisheries research

Subsistence resource or cultural recreational activity?

Is there demand for fresh and processed crab meat?

How can we culture freshwater crabs?

Sustainable Aquaculture and Fisheries

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