Puffinus opisthomelas breeds on five islands or small islets off the Pacific coast of Mexico (Guadalupe, San Benito East, San Benito Middle, San Benito West and Natividad) and on Isla Rasa in the Gulf of California. During the non-breeding season, it disperses along the Pacific coast from Monterrey and San Francisco bays (U.S.A.) and rarely British Columbia (Canada) in the north to the Gulf of California and further south to Nayarit, Jalisco and Colima (Mexico) (Carboneras 1992, Keitt et al. 2020).

Conservation Actions Underway
Natividad is a core area of the Vizcaino Biosphere Reserve, where there is some active management. In 1997-1998, goats and sheep were removed with the cooperation of the local fishing community (Keitt 1998). Cats were controlled in 1998, and eradicated by 2002 (B. Tershy and B. Keitt in litt. 1999, Keitt et al. undated). In 2016, the perimetral fence of the landfill was removed (Albores-Barajas et al. 2016). In 1998-1999, introduced herbivores were eradicated from San Benito (B. Tershy and B. Keitt in litt. 1999) and no invasive vertebrates were found on the island until 2006 (B. Keitt in litt. 2008). On San Benito Oeste, in 2006, a subspecies of the Cactus mouse Peromyscus eremicus (subspecies cedrosensis) was accidentally introduced; mouse eradication was successfully implemented in December 2013 and no mammals have been reported since (Sánchez et al. 2021b). Guadalupe is designated as a biosphere reserve (S.N.G. Howell in litt. 1998), and the process of eradicating the cats is underway.

Conservation Actions Proposed
Produce an up-to-date estimate of the population size. Assess the population trend. Quantify the impact of bycatch and other threats on the population size. Monitor the population trend.
Prohibit future road construction on Natividad. Control the access of visitors to middle and west San Benitos islands (B. Tershy and B. Keitt in litt. 1999). Remove rubbish or manage in a more efficient way (B. Tershy and B. Keitt in litt. 1999, Albores-Barajas et al. 2016). Prevent future introductions of native (gulls and ravens) and non-native predators. Ensure all breeding islands remain free of cats and exotic rodents (B. Tershy and B. Keitt in litt. 1999, Velarde et al. 2015). Protect breeding burrows from disturbance by dogs. Raise awareness for the species and its habitat with the aim of reducing anthropogenic disturbance to breeding colonies.