The Vaquita: Mexico's diminutive porpoise at risk of extinction

From the large and majestic humpback whale, mentioned in yesterday's post, we can travel to the other end of scale: the rare and diminutive Vaquita. Reaching a mere 5 feet in length, the vaquita is a member of the porpoise family and is only found in the northern end of the Sea of Cortez (Gulf of California). And at a scientific meeting of the International Whaling Commission being held in Agadir, Morocco, the findings of a 2008 population study show that there are only approximately 250 vaquitas alive today. As disturbing as that low number may seem, it is even more disconcerting when compared to a 1997 population study that estimated the population to be 567 - a decrease of 55% in just one decade.

The vaquita is similar to other small porpoise species that inhabit deltas and river outlets (one such species in China was considered extinct by 2007). Probably attracted to the shallows of the Sea of Cortez near the mouth of the Colorado River, the vaquita's habitat was impacted by the damming of the river in the U.S.; but researchers do not believe this has been a detriment to the vaquita. What appears to be the primary cause for the vaquita's decline is its tendency to get caught in the gill nets of local fishermen - a tragic victim of bycatch.

The 2008 population study represents the combined efforts of both Mexican and U.S. research groups with additional government support. To conduct the study required an elaborate high-tech version of a common biodiversity technique: to determine basic biodiversity, a transect is used to define an area and then sealife is counted within that area. Doing that several times over a wider area, estimates can then be extrapolated. For the vaquita population, several vessels were used to make large surface transects within which visual sightings and results from hydrophones (which picked up the distinctive clicking sounds made by the vaquitas) were tallied. From that raw data, the current population of 250 was estimated.

Although their primary range is now within a protected reserve, as of 2005, and includes a ban on the use of gill nets; the vaquitas are still very much at risk from illegal fishing. A lack of resources to provide effective enforcement combined with the economic needs of subsistence-level fishermen continue to put the vaquitas at risk. Plans are being considered to introduce fishing techniques that do not use gill nets, but getting local fishermen to abandon their traditional fishing methods will be challenging.

According to Nature News, "A more immediate challenge is to expand the protected area. 'We need to get all the gill nets out of the water,' says Timothy Ragen, executive director of the Marine Mammal Commission in Bethesda, Maryland. But a broader ban would be a difficult economic and political challenge, pitting the vaquita against the livelihoods of local fishermen."

The unique vaquita is one more cetacean that stands at the brink of extinction - not from industrialized commercial fishing or whaling, but from the needs of local fisherman trying to survive. This is dilemma being played out in many other parts of the world.

Read more in Nature News.