Global food demand is rising, and serious questions remain about whether supply can increase sustainably 1. Land-based expansion is possible but may exacerbate climate change and biodiversity loss, and compromise the delivery of other ecosystem services 2-6. As food from the sea represents only 17% of the current production of edible meat, we ask how much food we can expect the ocean to sustainably produce by 2050. Here we examine the main food-producing sectors in the ocean-wild fisheries, finfish mariculture and bivalve mariculture-to estimate 'sustainable supply curves' that account for ecological, economic, regulatory and technological constraints. We overlay these supply curves with demand scenarios to estimate future seafood production. We find that under our estimated demand shifts and supply scenarios (which account for policy reform and technology improvements), edible food from the sea could increase by 21-44 million tonnes by 2050, a 36-74% increase compared to current yields. This represents 12-25% of the estimated increase in all meat needed to feed 9.8 billion people by 2050. Increases in all three sectors are likely, but are most pronounced for mariculture. Whether these production potentials are realized sustainably will depend on factors such as policy reforms, technological innovation and the extent of future shifts in demand.

Cell-based seafood is an emerging novel food, with many start-up companies aspiring for ocean conservation benefits through expanded market share that displaces wild-caught seafood. However, the ability for cell-based seafood to achieve this conservation outcome is often oversimplified and will rely on an extensive, and we find somewhat tenuous, chain of events. Here, we outline the technological, behavioural, market and ecological changes that must occur along this pathway, and conclude that fisheries recoveries and collateral ocean benefits are unlikely to result from cell-based seafood technology. In particular, we detail nine necessary steps and argue that failure at any one step could hinder or even eliminate cell-based seafood's conservation effects. We additionally draw comparisons to aquaculture and share broader lessons for other demand-driven product interventions.

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Recent scholarship on unilateral presidential actions has recast our understanding of modern presidential policy making. However, our knowledge on this issue remains incomplete. In this article, the authors expand the literature on the unilateral presidency by exploring presidential proclamations from 1977 to 2005 (Presidents Carter to Bush) and identifying the importance of these tools as a policy-making instrument in expanding presidential power. By carefully examining the use of presidential proclamations, the authors discover that a majority of presidential proclamations involve presidential authority under congressionally delegated powers of international trade (and presidents most often use this authority to propose new trade arrangements or modify existing trade agreements), and they use this power in coordination with (but largely independent of) Congress. Presidents also use proclamations on the issue of national parks and federal lands exclusively to initiate new federal arrangements to establish new national parks or protections for federal lands, often against the will of Congress.

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