Small fish like sardinella are vital affordable protein sources in West Africa but are increasingly diverted for export and aquaculture feeds in wealthy regions, impacting local nutrition. While aquaculture, a fast-growing food sector, relies on marine ingredients like fishmeal and fish oil, wild fish catches are declining globally due to better management. These marine inputs remain important, especially for certain species, but supply is vulnerable to climate effects. Fish processing by-products now contribute significantly to fishmeal and oil production, improving sustainability. However, issues persist with sourcing tied to local food insecurity, highlighting the need for efficient, ethical, and locally attuned aquaculture feed strategies. Tools measuring nutrient conversion efficiency, such as Fish In: Fish Out ratios, can optimize resource use and bolster global food security.