Aquaculture is increasingly dependent on fishmeal and fish oil, but alternatives are emerging. The article discusses the trends in fishmeal and fish oil use in aquafeeds, showing reduced inclusion rates but increased total use due to higher aquaculture production and demand for fish high in long-chain omega-3 oils. The ratio of wild fisheries inputs to farmed fish output has fallen to 0.63 for the aquaculture sector but remains as high as 5.0 for Atlantic salmon. Various plant- and animal-based alternatives are now used or available for industrial aquafeeds, depending on relative prices and consumer acceptance. The outlook for single-cell organisms to replace fish oil is promising. With appropriate economic and regulatory incentives, the transition toward alternative feedstuffs could accelerate, paving the way for a consensus that aquaculture is aiding the ocean, not depleting it. Aquaculture is set to reach a landmark in 2009, supplying half of the total fish and shellfish for human consumption. With the production of farmed fish eclipsing that of wild fish, another major transition is underway: aquaculture's share of global fishmeal and fish oil consumption more than doubled over the past decade to 68% and 88%, respectively. This trend reflects rapid growth in aquaculture production and decreased use of fishmeal in the livestock sector in response to higher prices, but it belies significant improvements in aquaculture feed efficiencies. Impressive gains have been achieved in reducing feed conversion ratios (FCRs) for piscivorous fish and in substituting nonfish ingredients into formulated feeds. The volume of omnivorous species production has also risen, as seen, for example, in the transition in Asian shrimp farming from Penaeus monodon (piscivorous) to Litopenaeus vannamei (omnivorous). The ratio of wild fish input via industrial feeds to total farmed fish output (excluding filter feeders) has fallen by more than one-third from 1.04 in 1995 to 0.63 in 2007, a decline that underscores the expanding volume of omnivorous fish produced on farms and market pressures to reduce fishmeal and fish oil levels in aquafeeds. Nonetheless, serious challenges remain for lowering the aggregate level of fishmeal and fish oil inputs in feeds and alleviating pressure on reduction fisheries over time. The goal of this analysis is to illuminate the future path of feeds for producers, consumers, processors, retailers, and policymakers by evaluating the use of fish and nonfish alternatives. Given the significant quantities of fishmeal used to feed terrestrial animals (mainly swine and poultry), we also examine the relative efficiencies of protein conversion for aquaculture and livestock production. Searching for alternatives to fish-based feeds in an increasingly integrated world food system presents some tough choices. For example, is the use of rendered animal products (eAquaculture is increasingly dependent on fishmeal and fish oil, but alternatives are emerging. The article discusses the trends in fishmeal and fish oil use in aquafeeds, showing reduced inclusion rates but increased total use due to higher aquaculture production and demand for fish high in long-chain omega-3 oils. The ratio of wild fisheries inputs to farmed fish output has fallen to 0.63 for the aquaculture sector but remains as high as 5.0 for Atlantic salmon. Various plant- and animal-based alternatives are now used or available for industrial aquafeeds, depending on relative prices and consumer acceptance. The outlook for single-cell organisms to replace fish oil is promising. With appropriate economic and regulatory incentives, the transition toward alternative feedstuffs could accelerate, paving the way for a consensus that aquaculture is aiding the ocean, not depleting it. Aquaculture is set to reach a landmark in 2009, supplying half of the total fish and shellfish for human consumption. With the production of farmed fish eclipsing that of wild fish, another major transition is underway: aquaculture's share of global fishmeal and fish oil consumption more than doubled over the past decade to 68% and 88%, respectively. This trend reflects rapid growth in aquaculture production and decreased use of fishmeal in the livestock sector in response to higher prices, but it belies significant improvements in aquaculture feed efficiencies. Impressive gains have been achieved in reducing feed conversion ratios (FCRs) for piscivorous fish and in substituting nonfish ingredients into formulated feeds. The volume of omnivorous species production has also risen, as seen, for example, in the transition in Asian shrimp farming from Penaeus monodon (piscivorous) to Litopenaeus vannamei (omnivorous). The ratio of wild fish input via industrial feeds to total farmed fish output (excluding filter feeders) has fallen by more than one-third from 1.04 in 1995 to 0.63 in 2007, a decline that underscores the expanding volume of omnivorous fish produced on farms and market pressures to reduce fishmeal and fish oil levels in aquafeeds. Nonetheless, serious challenges remain for lowering the aggregate level of fishmeal and fish oil inputs in feeds and alleviating pressure on reduction fisheries over time. The goal of this analysis is to illuminate the future path of feeds for producers, consumers, processors, retailers, and policymakers by evaluating the use of fish and nonfish alternatives. Given the significant quantities of fishmeal used to feed terrestrial animals (mainly swine and poultry), we also examine the relative efficiencies of protein conversion for aquaculture and livestock production. Searching for alternatives to fish-based feeds in an increasingly integrated world food system presents some tough choices. For example, is the use of rendered animal products (e