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Why are vaquitas especially vulnerable to extinction?

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Illustration showing various cetaceans, including baleen whales like the blue whale, fin whale, humpback whale, gray whale, sei whale, northern right whale, and bowhead whale, as well as toothed whales such as the sperm whale, narwhal, beluga, Baird's beaked whale, killer whale, dolphins, and porpoises. Each species is labeled with its scientific name and typical or maximum length, with a size scale in the corner for reference. — cetacean Whales (order Cetacea).

The vaquita (Phocoena sinus), a cetacean and the smallest member of the porpoise family, is considered the most endangered marine mammal on Earth. Its extreme vulnerability to extinction is primarily driven by the following factors:1

Bycatch in Gill Nets: The primary threat is illegal gill net fishing in the Gulf of California. Because of their small size, vaquitas frequently become trapped as bycatch, which prevents them from surfacing to breathe.1
Illegal Totoaba Trade: The population has plummeted due to the expansion of illegal fishing for the totoaba, a fish whose swim bladders are highly valued in traditional medicine. The high market value of these bladders incentivizes illegal activity despite legal protections.12
Limited Geographic Range: The species is nonmigratory and restricted to a very small area in the northern Gulf of California, making the entire population susceptible to localized environmental and human-caused threats.1
Lax Enforcement: Despite government bans on gill nets, insufficient enforcement of the law has allowed the continued use of these lethal nets, leading to a population decline of approximately 98 percent between 1997 and 2018.1