Overfishing happens when you take more fish out of the ocean than it can naturally restock. Species cannot replenish, therefore causing resource depletion, reduced biological growth rates and low biomass levels. Long term overfishing can lead to critical depensation and it's one of the leading causes of nature declines today.
According to the Food and Agriculture Organization of the United Nations, the amount of overfished stocks around the world has tripled in half a century. Today, one-third of the world's assessed fisheries have pushed beyond their biological limits. The damage done by overfishing will not only impact our marine ecosystems, but also billions of people who rely on fish for protein and their livelihood.
"Fishing Down" happens when commercial fleets began traveling deeper in the ocean and farther down the food chain for viable catches after the collapse of large fish populations, and it has triggered a chain reaction that is upsetting the ancient and delicate balance of the sea's biologic system.
For example, coral reefs will be particularly vulnerable to overfishing. Plant-eating fish eats algae and keeps the coral clean and healthy so that it can grow. Fishing out too many herbivores can weaken reefs and make them more susceptible to being ravaged by extreme weather events and climate change. Fishing equipment and debris can also physically destroy the fragile corals that make up the reef foundations.
Trawling, a method in which boats pull massive nets behind them in the water, pulls in more than just shrimp and bluefin tuna - it captures just about anything in its path. Sea turtles, dolphins, sea birds, sharks, and other animals have all faced existential threats as bycatch.