Forty-two urine and 96 blood and serum samples were obtained from California sea lion (Zalophus californianus) pups from the Gulf of California during the 2000 reproductive season. Antibody prevalence to 13 serovars of Leptospira interrogans was determined by microagglutination tests (MAT); presence of pathogenic leptospires was detected by polymerase chain reaction (PCR). Samples with antibody titers > or = 1:25 or 115 bp fragments on ethidium bromidestained 1.5% agarose gels were considered positive. Antibody prevalence was 54% overall with highest prevalence against serovar cynopteri (50% of all positive reactions). Highest antibody titers (1:50) were detected against serovars cynopteri and pomona. Polymerase chain reaction products were observed in two of 42 urine samples, six of 96 blood samples, and one of 96 serum samples. Presence of PCR products in blood and serum was demonstrated in pups that were seronegative. Kruskall-Wallis tests and corresponding post hoc Tukey tests (alpha = 0.05) showed that prevalence of leptospirosis was significantly different among all rookeries. The high seroprevalence (54%), low antibody titers (maximum 1:50), absence of pups showing clinical signs indicative of the disease, and lack of recent reports of increased mortality of sea lions in the Gulf of California are suggestive of the presence of enzootic host-adapted serovars. Crowding in rookeries as well as the presence of bats and rodents on some of the islands may explain infection by L. interrogans (sensu lato) and some of the differences in seroprevalence among reproductive rookeries.

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.