The SPLASH project (2004)(2005)(2006) revealed complex population structure and migratory connections, but no regional effort was made along the southern Mexican Pacific coast until dedicated research was initiated in 2010. It is unclear
This note constitutes the first report of the Guadalupe fur seal (Arctocephalus townsendi) for Oaxaca. This subadult male was found stranded on a beach in Cerro Hermoso, in the Lagunas de Chacahua National Park (PNLC). This record is highly relevant because the normal range for this fur seal is farther north, in Guadalupe Island and a recolonization site in the San Benito Archipelago, more than 1,300 km from the stranding location. This is the southernmost report for A. townsendi and the first case for Oaxaca, increasing the number of known marine mammal species for this area in the Mexican South Pacific. Because of the current population growth of this otariid, we highlight the necessity of tracking these atypical sightings over time. All Rights Reserved
Knowledge of the alpha diversity contributes to the determination of conservation priorities by identifying regions with high species richness and/or a large number of endemic, rare, or endangered species. The present study focused on the evaluation of species richness and composition of the marine mammal community off the coast of Oaxaca. A total of 293 surveys were carried out between December 2011 and April 2015. Additionaly, observation and stranding records found in the literature and zoological collections (corresponding to the period 2008-2014) were revised to estimate alpha diversity. The results allowed us to conclude that the current richness of marine mammals for the state, comprises 21 species distributed in 2 orders, 3 suborders, 5 families, and 17 genera. This represents a 75% increase in the known richness prior to this study. All species of marine mammals are found in some risk category according to the NOM-059-Semarnat-2010 (Mexico), IUCN, and CITES. Our results highlight the importance of the Oaxaca region in the Mexican South Pacific as a priority area for conservation, because of its high degree of richness, considerable diversity in species composition, and the concentration of vulnerable or endangered marine mammals.
To date, few studies have focused on the Bryde's whale, Balaenoptera edeni, one of the eigth species comprising the family Balaenopteridae. This species can be distinguished from other rorquals by the presence of three parallel longitudinal ridges on top of the rostrum, whereas other rorquals possess only one. The potential distribution of this species in the Mexican Pacific is thought to extend south from 26° N, along the coast of Mexico from Baja California to the border with Guatemala. Our knowledge about this species in the Mexican South Pacific is limited, particularly off the coast of Oaxaca where no previous sightings have been reported. The sightings were recorded during oceanic trips to monitor humpback whale (Megaptera novaeangliae) migrations off the central coast of Oaxaca, Mexico, between December 2011 and January 2012. The observation platforms were 6 m fiberglass boats with a 60 hp outboard engine. The geographical coordinates were registered with a handheld GPS; also recorded were sea surface temperature and the behavior of rorqual specimens. The initial species identification was based on the presence of three parallel longitudinal ridges on the head, and was subsequently corroborated by comparing the photographs and video taken during the sightings with field guides. Four separate rorqual sightings were documented between 1.3 and 7.1 km from the coast of Estacahuite, Zipolite, and Ventanilla, Oaxaca, Mexico. Two sightings involved groups with calves; during one sighting, three killer whales, Orcinus orca, were also observed, although neither predatory behavior nor other interaction occurred. The behaviors observed included breaches by calves, surface activity, and slow and erratic movements with sudden changes of direction in response to the presence of the research boat. During surface exhalations, one individual produced vocalizations that were audible at the surface. The presence of B. edeni off the central coast of Oaxaca, Mexico, may be associated with the oceanographic characteristics and high productivity of the Gulf of Tehuantepec. All behaviors observed during the sightings were typical of the species, including evasive maneuvers and sudden changes of direction with respect to the boat. The fortuitous recording of audible vocalizations clearly recognizable from the research boat during surface exhalations is remarkable. These sightings are the first reports of B. edeni for the state of Oaxaca and the Mexican South Pacific. Thus, there is a clear need to increase intensive, long-term monitoring efforts in order to better understand the ecological implications and other aspects related to the presence of the Bryde's whale and other marine mammals in the region. Future research should focus on assessing the spatial and temporal occurrence of B. edeni in this region.
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