The vaquita, a rare porpoise restricted to the northern Gulf of California, could very soon join the baiji as another cetacean species driven to extinction by humans, according recent studies.
The plight of the vaquita (Phocoena sinus), also known as the Gulf of California porpoise, was highlighted in a recent issue of the journal Conservation Biology by Armando Jaramillo-Legorreta, Lorenzo Rojas-Bracho, Robert Brownell, Andrew Read, Randall Reeves, Katherine Ralls and Barbara Taylor.
According to the authors, there are only about 150 individuals remaining (with the greatest threat being bycatch mortality), and it would only take about two years before the population diminishes to the point of no return.
Captive breeding not a solutionThe authors reason that aptive breeding will not be a solution. Although some species have been saved by captive breeding when very few individuals remained, captive breeding is not feasible for vaquitas.
Safely capturing these small, cryptic, solitary, and elusive animals in relatively deep water would be extremely difficult, and even if it were possible, maintaining other marine porpoises (Phocoenidae) in captivity in good health over long periods has proven difficult.
Captive vaquitas would likely have a high rate of initial mortality, as seen with other small cetaceans such as baiji (Lipotes vexillifer), Delphinus, and Platanista, and, as with other wild species taken into captivity, some of the survivors would not reproduce.
Furthermore, experience with other species has shown that captive-bred individuals often lack behaviors needed for survival in the wild and consequently have a poor survival rate when reintroduced. Thus, an in situ approach has the best chance of saving the species because the food base is still excellent, and there are no serious threats other than bycatch....
Ban on net fisheriesThe only viable solution available would thus be to impose a total ban on entangling net fisheries.
However, time might be running out even for this option: s it will take time to plan and raise money to buy out entangling net fisheries, the first step in 2008 must be to find funds to establish a total fishing moratorium on all entangling nets so that vaquita mortality can be immediately reduced to zero.
Most important, there is very little time remaining until the population will be so small that it will be vulnerable to stochastic events or processes (ecological, genetic, and demographic).
The authors conclude that the imminent extinction of the vaquita ...would represent another failure of our community of scientists to explain in simple terms the plight of a critically endangered species and thus convince decision makers to act decisively and urgently.
For more information, see the paper: Jaramillo-Legorreta, A, L Rojas-Bracho, RL Jr. Brownell, AJ Read, RR Reeves, K Ralls, BL Taylor (2007) Saving the vaquita: immediate action, not more data. Conservation Biology 21, pp. 1653"1655.