General Fisheries Commission for the Mediterranean - GFCM

Non-indigenous species and fisheries in the Mediterranean Sea | The case of the blue crab


The ecosystem of the Mediterranean and the Black Sea has changed significantly over the last few decades due to the introduction of non-indigenous species, also commonly called alien species. With over 900 non-indigenous species in the Mediterranean Sea and almost 300 in the Black Sea, fisheries are adapting to take into account the ever-changing marine ecosystem. 

During the first half of the twentieth century, the voracious blue crabs appeared in the Mediterranean. With their large populations expanding rapidly across the basin, concerns were raised over their impacts on local ecosystems, and their negative interactions with existing fisheries, as blue crabs get stuck in artisanal fishing nets and creates important losses in catch and net replacement.

Yet soon, the large size and good palatability of the American blue crab (Callinectes sapidus) and the blue swimming crab (Portunus segnis), made them in turn the object of fisheries. Dedicated strategies are being developed to control the populations and commercialize the catch, including designing tailor-made fishing gear and creating new profitable market niche. 

To learn more about the ecology of these species and to understand how to control their expansion by means of sustainable coastal fisheries, the GFCM is launching a research programme that will help to understand how blue crab fisheries can be developed and managed based on the most recent scientific data.  

Mediterranean countries will soon join a regional research programme on blue crabs  

The GFCM research programme on blue crab is expected to build upon ongoing research activities, enabling the sharing of knowledge among all stakeholders involved in blue crab fisheries: fishers, managers, scientists, environmentalists, economists, and all relevant experts. Countries such as Egypt, France, Greece, Spain and Tunisia are already addressing these species and are expected to join the research programme, together with research institutes and individual scientist interested in the topic. The objective of the research programme is to set up a coordinated framework for the sustainable management of blue crab fisheries, based on scientific evidence and agreement on measures to implement, in a way that both fisheries and environmental objectives are taken into account.  

In this way, fisheries could act as a tool to keep blue crab populations under control while providing opportunities for the fishing sector. This implies decreasing levels of unwanted environmental changes and damages, while also keeping blue crab fisheries within sustainable environmental and economic levels. 

The research programme will be structured in a series of work packages, according to six specific objectives:  

  • Work package 1 – Biology and ecology  
  • Work package 2 – Fishery-independent data collection  
  • Work package 3 – Fishery-dependent data collection  
  • Work package 4 – Stock assessment  
  • Work package 5 – Blue crab fisheries: fishing technology, socio-economic elements, and value chain  
  • Work package 6 – Management proposals 

The research programme is expected to feature the collaboration of partners from all Mediterranean subregions, particularly from those countries where blue crab fisheries are already developed though to different degrees. 

The need for scientific data on the dynamics of non-indigenous species 

Reliable scientific data on the dynamics of non-indigenous species distribution and abundance are essential to understand their ecological and economic effects. Given the important dispersion of non-indigenous species in the region, the GFCM recently published Non-indigenous species in the Mediterranean and the Black Sea - GFCM Studies and Reviews 87. This review – in addition to providing images and descriptions of relevant species to aid in identification – presents a unique historical and regional perspective on these species’ impacts, based off many years’ worth of research. Future studies and programmes can build upon this comprehensive source of information. 


Learn more about the publication. 

Learn more about the GFCM’s research programmes. 

Learn more about Recommendation GFCM/42/2018/7 on the regional research programme on blue crab in the Mediterranean Sea