This is bad: a recent assessment by the International Union for Conservation of Nature (IUCN) reported that 25% of the 1000-or-so species of sharks and rays are in danger of extinction. Add to that 18% of the world’s grouper species, and that’s a whole lot of top-level predators becoming rare in the ocean.
This is bad, and not just because it means there are fewer tasty fish for us to eat. Overfishing even a single species is increasingly leading to snowball effects that trickle through the ecosystem. Don’t think that predators are all that important? Check out how the reintroduction of wolves to Yellowstone moved rivers: