The protected area of the Moulouya River mouth, also known as a SIBE (Site of Biological and Ecological Interest), is one of the most important and vulnerable freshwater reserves in the southern Mediterranean. This site is characterized by a wide variety of habitats that support rich aquatic biodiversity with a high degree of endemism. It was also one of the first wetlands in Morocco to be invaded by the marine and invasive American blue crab, Callinectes sapidus Rathbun, 1896, following its initial establishment in the Marchica Lagoon. Since its first detection in 2019, the blue crab has been expanding its range upstream in the Moulouya River, now reaching areas home to some of the last populations of endemic and patrimonial species in Eastern Morocco. In this paper, we compare the abundance of certain patrimonial species in the Moulouya SIBE before and after the arrival of the blue crab, focusing on the Moroccan endemic freshwater mussel Unio foucauldianus Pallary, 1936, and the freshwater crab Potamon algeriense Bott, 1967. We observed a complete disappearance of these species in certain areas of the lower Moulouya, which could likely be attributed to predation by the blue crab. The predation and migration behaviour of the blue crab in the Moulouya River aligns with what has been described in the literature for its non-native range.

Biological invasions threaten biodiversity worldwide. The American blue crab Callinectes sapidus Rathbun, 1896, among the Mediterranean’s most damaging invaders, takes up the challenge to transform this threat into gain. To turn its impact into economic value and guide control efforts, we analysed separately the meat composition and exoskeleton biopolymers of adult crabs from three Moroccan protected Sites of Biological and Ecological Interest: Marchica Lagoon (S₁), Moulouya Estuary (S₂), and Al Hoceima National Park (S₃). Marchica specimens exhibited the highest protein content (21.87 ± 1.15 g 100 g⁻¹, p < 0.001) and an elevated lipid fraction, yielding nutrient-dense meat suitable for premium markets. Moulouya crabs were noted for their taste potential, with a higher concentration of fat (1.73 ± 0.09%) and carbohydrates (0.91 ± 0.1%). Al Hoceima individuals displayed markedly mineralised exoskeletons producing lean and low-fat meat, valued in dietary applications. Exoskeleton organic-to-mineral (OM/MM) ratios and proximate composition revealed three adaptive profiles, opportunistic (S₁), acclimatory (S₂), and conservative (S₃), presumably correlated to local salinity, productivity, and substrate conditions, underscoring the species’ phenotypic plasticity. X-ray diffraction confirmed the α-chitin polymorph, while FTIR analysis indicated degrees of deacetylation consistent with high-purity chitosan. These findings support the development of a site-specific circular economy framework and may contribute to the ecological resilience of Morocco’s protected coastal areas.

The Mediterranean Sea is experiencing an increased impact of biological invasions, including along the coastlines of North Africa. The non-indigenous sponge Paraleucilla magna Klautau, Monteiro & Borojevic, 2004 was detected recently in the western Mediterranean coast of Morocco. In this paper we document for the first time the occurrence of this non-indigenous species (NIS) in Marchica Lagoon, a Ramsar site and protected area situated on the eastern Mediterranean coast of Morocco. Additionally, we report it from the Saidia Marina, the easternmost location in the country where the species has been found, demonstrating its rapid expansion. The Marchica lagoon and Saidia marina have become hotspots for the proliferation of NIS, underscoring the pressing need for monitoring and management strategies to address the issue of biological invasions in this region.