Northern krill Meganyctiphanes norvegica as a sustainable mesopelagic source of high-quality protein: a systematic review of challenges and opportunities

Krill ( Euphausiacea ) exists in all the oceans and climates on the planet and comprises 86 known species, having small overall size (lengths between 2 and 7 cm), from which some inhabit the mesopelagic zone. Mesopelagic organisms (fish, crustaceans, and squid) represent some of the world’s largest understudied and untapped resources, rich in marine omega-3 fatty acids and high-quality protein. Among all krill species, mostly Antarctic krill Euphausia superba (AK) and Pacific krill E. pacifica have been systematically studied, due to relatively large sizes, significant biomass estimations and available commercial exploitation. Three more species have also small-scale exploitation in Japan ( E. nana, Thysanoessa inermis and T. raschii ). The current systematic review has been carried out by two scientists in line with the international PRISMA 2020 standards to analyze the available knowledge on Northern krill Meganyctiphanes norvegica (NK). Concretely, the aims of the review were to summarize the knowledge on biomass of NK worldwide, its ecological role, to discuss the potential for sustainable harvesting and local processing of NK as high-quality nutritional source and identify the major knowledge gaps which would require further research. Our study identified insufficient long-term population studies and climate change effects on these, often incomparable results on biomass estimation between studies, lack of bioactivity and toxicity data on NK protein concentrates and oil extracts, best processing methods from food safety point of view. All these knowledge gaps urgently need further addressing prior to any possible uses of any NK fractions as alternative ingredients for human consumption. The main constraint to biorefinery establishment for NK and mesopelagic fish is not availability of suitable fractionation chemistry and downstream processing approaches but responsible biomass access.