Overfishing is when we catch too many fish and marine animals at sea. Especially if they are of one species and fished at such a rate that the species cannot recover to normal numbers. Overfishing reduces the numbers of some species so much that their survival is threatened. This causes problems for other species that feed on them, or are otherwise connected. Poaching with prohibited techniques (e.g. trawling) or during the species' breeding season is also very destructive.