Although all marine mammals are protected by laws in the U.S. and many other nations, dolphins and porpoises frequently drown in fishing nets. The Vaquita, a tiny harbor porpoise found only in the upper Gulf of California, may soon be extinct, primarily because of constant incidental mortalities in the tutuava fishery. Scientists and the fishing industry are working to develop new methods of fishing that reduce bycatch. One technique is to attach pingers to the fishing nets that emit beeping sounds to alert dolphins of the net's presence.
Marine debris is also a serious problem.
Dolphins can ingest or become entangled in litter, such as discarded ropes, monofilament fishing line, and plastics. We can prevent this problem by recycling and eliminating litter. Occasionally, there are large mortality incidents involving dolphins. For example, several thousand striped dolphins washed ashore in the Mediterranean Sea in 1990-1992. In both cases, the cause was a virus called Morbillivirus.