To overfish means to catch so many fish from an ocean, lake, or river that not enough remain to reproduce and maintain healthy populations. When people overfish, they're taking fish faster than nature can replace them.

Imagine a pond with 100 fish that have 50 babies each year. If you catch 40 fish annually, the population stays healthy. But if you catch 80 fish each year, the pond empties. That's overfishing: removing fish faster than they can replenish themselves.

Overfishing has become a serious problem in Earth's oceans. Modern fishing boats can catch thousands of fish at once using enormous nets. Some fish populations, like Atlantic cod off Canada's coast, collapsed from overfishing in the 1990s. When a fishery collapses, it means so few fish remain that fishermen can't catch enough to make a living, and the fish population struggles to recover even when fishing stops.

The ocean can seem limitless, making it easy to assume fish populations will last forever. But overfishing proves that even vast natural resources have limits. Scientists now work with fishing industries to set catch limits that allow fish populations to survive and thrive. When fishing is managed responsibly, both the fish and the fishermen can flourish for generations.