If the stalls of the fish sellers in the Old Port market offer a great variety, it is partly thanks to the efforts made locally to recreate biodiversity. Off Marseille, the former mayor Jean-Claude Gaudin built what he considered the 112th district of the city: the largest site of artificial reefs in Europe with more than 400 concrete structures imitating coral habitats immersed 82 ft (25 m) below the surface of the sea. These marine life incubators have enabled the maritime fauna and flora to reassert themselves over ten years. The number of fish has tripled, and the biodiversity has increased by 30% throughout the site, notably with the return of certain flagship species such as sea breams, red mullets, lobsters, groupers, or conger eels. Some 70 species inhabit these reefs today compared to 24 in 2010. Such a spectacular development was rewarded by the National Grand Prize for Ecological Engineering of the Ministry of Environment.