There is a certification group called Best Aquaculture Practices[0] that sets standards for hatcheries, farms, feed mills, and processing plants regarding sustainability and quality. They've got a new feed mill standard[1] but it seems like it gives feed mills a few years to come into compliance to use sustainable fishmeal and fish oil.

[0]https://bapcertification.org/Home [1]https://bapcertification.org/Downloadables/pdf/standards/BAP...