According to the WWF Living Planet Report, released in 2018, almost 6 billion tonnes of fish and other seafood had been removed from the oceans since 1950 and in the current century, freshwater fish faces the highest extinction rate among other species of vertebrates.

Fishing is known to be the greater cause of change in many ecosystems, but it remains to be studied how exactly removal of those predators affects aquatic ecosystems - although, as pointed out by Marten Scheffer in a study in 2015, the responses of different environments my change greatly.

The importance to understand deeply the huge fisheries impact to a global scale can be explained when considering that billions of people rely on oceans to provide jobs and food, besides other services. Only considering food, circa 4.3 billion people rely on fish as protein intake source and a collapse in this system could be catastrophic.

A real problem pointed out by several ecological organizations is "Overfishing", which is when fish are caught faster than they can reproduce, reducing the size of the fish stock. Already by 2002, FAO claimed that 47% of the fish stocks were fully exploited. And some species, as pointed out by WWF, like bluefin tuna and Grand Banks cod are experiencing a great population decline due to fishing. 

Illegal fishing, also contributes to negative impacts, as 85% of fish stocks are under the risk of illegal or irregular fishing.

Additionally, some fishing techniques are considered destructive to the habitats where they are used, linking the practice to biodiversity loss due to habitat destruction. Below, you can watch a short video on those practices: