Twilight zone fish move carbon to the deep ocean, but fishmeal fishing may put that at risk

Every night, billions of twilight zone fish rise from about 300 meters deep to feed near the surface, then return to depth. Their waste carries carbon from surface waters into the deep ocean, where it may stay out of the atmosphere for long periods. Researchers estimate the twilight zone fish community at around 10 billion tons, close to 90% of ocean fish biomass. That carbon pathway is still poorly understood, but commercial fisheries are already exploring these fish as a source for animal feed. Expanding that catch before the science is done could disrupt a natural carbon storage system. The article explains why researchers are racing to learn more and why the outcome matters for both biodiversity and climate.