The red swamp crayfish (Procambarus clarkii) has become one of the most widespread and problematic alien invasive species in the rivers of the Iberian Peninsula. However, its recreational fishing for self-consumption as a seasonal product is deeply rooted in rural areas throughout Spain. As a food product, this crayfish could be considered a healthy ingredient that provides a variety of nutritional benefits. However, it also tends to bioaccumulate large amounts of environmental contaminants in its tissues. Thus, its monitoring is of critical importance if food safety hazards, are to be prevented, especially in aquatic ecosystems affected by the presence of abandoned mining residues that have never been remediated.
A research led by the Wildlife Toxicology Group of the Spanish Institute of Game and Wildlife Research (IREC – CSIC, UCLM, JCCM) has evaluated the food safety risk associated with the consumption of crayfish from the stretches of Valdeazogues and Montoro rivers, in the Province of Ciudad Real (Spain), that flow, respectively, within the former Almadén Mining District(the largest mercury (Hg) producing area in the world until late 20th century), and within the forme Alcudia Valley Mining Distric(the main lead (Pb) producing area in Spain until late 19th century).
The results indicated that populations of crayfish in the Valdeazogues and Montoro rivers accumulate the Hg and Pb pollution respectively, that persists in these two historical mining districts. The Maximum Residue Levels established by the European Union legislation on food safety for total Hg and Pb in the muscle meat of crustaceans were exceeded by 27% and 87% of the abdominal muscles of crayfish from the Valdeazogues and Montoro rivers, respectively . Risk indices indicated that, even after adjusting for bioavailability (the fraction of the ingested metal that is absorbed at the gastrointestinal level, which was approximately 28% for Hg and 34% for Pb in the tail muscle), it is not safe to consume crayfish from these rivers because of their high levels of Hg and Pb, especially for children. The cooking procedure of the whole crayfish body (tail muscle, carapace and viscera in the cephalothoracic cavity) following a typical Spanish recipe for crayfish had a very limited effect on the total concentration of metals in the crayfish body burden, extracting 9% of Hg and 2% of Pb, approximately. Nevertheless, given the high levels of metals accumulated by crayfish from these mining districts, it is not recommendable to use them as a condiment or ingredient for flavouring.
Recreational crayfish fishing is already restricted in most of the river section flowing within the Almadén Mining District, but advisory signs regarding this restriction have not been installed in the area . On the other hand, crayfish fishing in the Montoro River On the other hand, crayfish fishing in the Montoro RiverThe results of this investigation recommend the implementation of management measures and the development of environmental communication campaigns aimed at preventing food safety risks associated with the consumption of crayfish from these mining districts. Likewise, further attention must be paid to the role of this invasive crayfish as a major vector of environmental pollutants to higher trophic levels, since it has become a highly important prey for tens of mammal (such as the Eurasian otter,Lutra lutra), and bird species within the native predator community whose conservation could be threatened by the biomagnification of mining pollution.
Rodriguez-Estival, J., Morales-Machuca, C., Pareja-Carrera, J., Ortiz-Santaliestra, M. E., Mateo, R. 2019. Food safety risk assessment of metal pollution in crayfish from two historical mining areas: Accounting for bioavailability and cooking extractability Ecotoxicology & Environmental Safety 185, 109682.