Ghost net

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Ghost nets are fishing nets that have been lost by fishermen. These nets are left to drift the oceans of Earth entangling sea life and causing havoc throughout Earth's oceanic ecosystem. A vast array of sealife is harmed by these lost nets, harming both vertebrates and invertebrates, including many different species of marine mammals.

Many commercial fishing nets operate as 'gillnets'. These are deployed as a 'wall', creating a vertical plane, often up to half a kilometre across, through which any fish within a certain size bracket will become caught and die. Normally, after a certain period, these nets will be collected by fisherman and the catch removed. However if this is not done (the nets become lost to storms, forgotten, etc.) the net will continue to catch fish until the total weight of the catch becomes larger than the buoyancy of the floats. The net will thus sink, and the fish devoured by bottom-dwelling crustaceans and other fish. Soon, with the weight on the net reduced, the floats will pull the net up again. This repeats itself until the net is destroyed or entangled on the sea floor. Given the high-quality synthetics that are used by commercial fishing operations throughout the modern world, such destruction can take decades.

Although normally considered a priori 'wrong', it is often stated that such nets have a negligible impact upon marine ecosystems, as the catch of the ghost net is simply eaten by other marine life anyway.