Drift nets are used in large-scale commercial fishing operations. Miles-long in length, nets are suspended from floats at various depths and set adrift in open oceans to capture fish or squid. Drift nets are constructed of a light, plastic monofilament that resists rotting. These nets are generally of a type known as gill nets, because fish usually become entangled in them by their bony gill plates. The fishing industry has found these nets to be cost-effective, but their use has become increasingly controversial. They pose a severe threat to many forms of marine life, and they have long been the object of protests and direct action from a range of environmental groups. National and international policies concerning their use have only recently begun to change.

Drift nets are not selective; there is no way to use them to target a particular species of fish. Drift nets...