2003, a scientific report estimated that only 10 percent remained of the large ocean fish populations that existed before commcrcial fishing began. Specifically, commercial fishing has greatly reduced the number of Large predatory fish' such as cod and tuna Today, there are plenty of fish in the sea, but they're mostly just the ittle ones. Small fish, such as sardines and anchovies, have more than doubled in number-largely because there are not enough big fish to eat them