Unsubstantiated Claims Can Lead to Tragic Conservation Outcomes Bioscience

The vaquita porpoise (Phocoena sinus) is Mexico's only endemic—and the world's most endangered—marine mammal. With a population of fewer than 30 individuals (Thomas et al. 2017, IUCN 2018), any delay in taking needed conservation actions will result in its extinction. A recent article in the journal Sustainability (Manjarrez-Bringas et al. 2018) reasserts, without providing any scientific evidence, the baseless claims that the vaquita is fundamentally an estuarine species and that decline in vaquita is due to reduction of freshwater flow into the Upper Gulf of California (UGC) due to damming and diversion of the Colorado River. These unsupported claims detract from the real cause of vaquita decline—deaths in gillnets, in both legal and illegal fisheries. Here, we focus on setting the record straight, again, that there is no evidence that damming of the Colorado River has affected the fate of vaquita, in the hope that management efforts can be correctly and effectively directed to protect this marine mammal. As we describe below, the Upper Gulf did not have a large, long-term, continuous river flow nor brackish-water conditions even before the damming of the Colorado River.