Three gaps in governing the mesopelagic for human nutrition

The mesopelagic is one of the most biomass-rich marine ecosystems on the planet and it contributes to mitigating climate change and supports marine food webs globally. Deep-sea fishing is a growing threat for the ecosystem, yet, fishing may contribute to increasing human nutrition by feeding aquaculture production. Here, we used and matched species nutritional and aquaculture data, and a comprehensive dataset of ocean-related international agreements, first, to assess potential implications of mesopelagic fishing for human nutrition and second, to evaluate the extent of mesopelagic governance in international policies. We found that the contribution of mesopelagic fish (feeding into aquaculture) to reduce human nutritional vulnerability would be marginal. In addition, major gaps in the international governance of the mesopelagic remain, including an absence of acknowledgments and mentions in ~70% of international policy documents, little reference to mesopelagic species, and fragmented coverage of the mesopelagic habitat by policies. Our work suggests that without substantial advances in ocean policies, the world's largest fishery by harvestable biomass would be developed without a clear indicationof its benefit for humanity and with legal gaps threatening its sustainability from the onset.