Bycatch is the single biggest threat to the survival of the few remaining vaquita. Some commentators believe the measures fall short of what is needed to save the vaquita. A dissection of a beached Vaquita showed remains of squid and grunts. Operation Milagro is an ongoing operation to save the vaquita porpoise from extinction. Many porpoises, mainly the vaquita, are subject to great mortality due to gillnetting. Porpoises range in size from the and Vaquita to the and Dall's porpoise. Toothed whales range in size from the and vaquita to the and sperm whale. Because the vaquita was only fully described in the late 1980s, historical abundance is unknown. The vaquita is listed as Critically Endangered on the IUCN Red List. Found only in Mexico's Gulf of California, the once numerous vaquita are now critically endangered. The vaquita ("Phocoena sinus") is a species of porpoise endemic to the Gulf of California. The vaquita porpoise, discovered in 1958, has become the most endangered marine species. The smallest cetacean, which is also (as of 2006) the most endangered, is the vaquita. Vaquita die in gillnets set to catch totoaba (the world's largest drum fish).