Solving Ariadne’s thread in the blue crab invasion to turn it to a true paradigm of circular economy: eco-biological traits and valorization of by-products to enhance fisheries value, a scoping review

The blue crab (Callinectes sapidus) is among the 100 most harmful invasive species worldwide and was introduced to the Mediterranean in the mid-20th century via shipping, causing major ecological and aquaculture harmful consequences. Similar to Ariadne’s thread resolution to the labyrinth through an encyclopedic operation of logic towards all viable routes, the key to resolving the problem of blue crab’s invasion is to support the main predation potential, i.e., human consumption. This review examines the ecological, biochemical, and molecular basis of this successful invasion and proposes circular valorization of blue crab by-products as a strategy to convert the invasion into a market opportunity. Under climate change, adaptive traits of C. sapidus indicate stable establishment and further spread, suggesting that its exploitation could lead to ecological balance. However, because of consumer attitudes and European Union (EU) regulations, blue crab fisheries remain underdeveloped despite its high nutritional value, while some catches are even exported back to their native range. Apart from the high meat quality, blue crab’s shell, an element usually considered as waste, constitutes a source of high valued by-products such as chitin and chitosan, which represent bio-active compounds for the food industry. Shell-derived carotenoids and CaCO3 can stand as a supplement in poultry feeds and in fish feed coloration where it is needed, as it does in salmon. Since processing methods generate waste that may exceed 80% of the total biomass, turning this waste into high-value products may result in transforming this invasive species into a high valued fisheries source.