The oceans are losing oxygen at an unprecedented rate and this poses a major risk to tuna, sharks and other species. The findings were presented by the International Union for the Conservation of Nature at the UN climate conference in Madrid. They shared that "the delicate balance of marine life is thrown into disarray" as the ocean loses oxygen. While all fish need oxygen to survive, the bigger species are more vulnerable to these depleting levels as they need more oxygen to survive. They are thus moving towards the shallow areas of sea, where they are vulnerable to fishing. Global heating is a major source of this depleting oxygen levels.