If only there were plenty more fish in the sea. A study titled “Declining diversity of wild-caught species puts dietary nutrient supplies at risk” suggests that a decline in the biodiversity of fish available for consumption can negatively affect the diets of those who get a fair amount of their protein from swimmers.

The study was led by Cornell and Columbia University researchers, published in Science Advances and based on the Loreto region of the Peruvian Amazon. Citizens there eat high amounts of fish, but the types of species they’re now consuming are changing. That’s because catches of some varieties of fish that are high in certain nutrients are declining. To safeguard biodiversity and improve food security for billions of people, important steps need to be taken, including establishing and enforcing “no-take zones”—areas set aside by governments where commercial fishing is off-limits to allow fish stocks to rebound.

See also: There Is Something Fishy About American Seafood