Vaquita often are caught in nets set to catch other animals. This "incidental take" is the primary reason for the vaquita's endangered status. Gulf of California fisheries include shrimp trawling and gillnet fisheries for sharks. (A gillnet is a large flat fishing net that entangles fish as it hangs vertically in the water.) Each year, 25-30 vaquita drown in gillnets.

Vaquita survival is closely related to one gillnet fishery in particular: totoaba (Totoaba macdonaldi, a type of fish resembling the white seabass). Like the vaquita, the totoaba lives only in the upper Gulf. Vaquita are easily entangled in the larger holes of the totoaba nets. In 1990, the International Whaling Commission (IWC) determined that the totoaba fishery is responsible for the vaquita's endangered status.

Totoaba is itself an endangered species. For many years, totoaba fishing continued with no controls. Even small-scale totoaba fishing was very difficult to monitor. Mexico banned totoaba fishing in 1975. The U.S. has banned imports of totoaba since 1977. But demand for totoaba as a food fish keeps the illegal fishery profitable.

Laws in both the United States and Mexico protect the vaquita. It was placed on Mexico's endangered species list in 1978. The U.S. added the vaquita to its endangered species list in 1985. A vaquita sanctuary was established in the northern Gulf area. But as long as illegal totoaba fishing continues, vaquitas will continue to drown in gillnets. If people continue to buy totoaba, not only will this fish become extinct, so will the vaquita.

Nowak, Ronald M. (ed.). Walker's Mammals of the World. Vol. II. Baltimore: Johns Hopkins University Press, 1991.