Vaquita Face Extinction from Bycatch. Comment on Manjarrez-Bringas, N. et al., Lessons for Sustainable Development: Marine Mammal Conservation Policies and Its Social and Economic Effects. Sustainability 2018, 10, 2185

Abstract

We are among the scientists who have documented the environmental and ecological changes to the Upper Gulf of California following the reduction in the Colorado River’s flow. We object to any suggestion that our research supports Manjarrez-Bringas et al.’s conclusion that the decline in the Colorado River’s flow is the reason for the decline in the population of the endangered vaquita porpoise (Phocoena sinus). Manjarrez-Bringas et al.’s conclusions are incongruent with their own data, their logic is untenable, their analyses fail to consider current illegal fishing practices, and their recommendations are unjustified and misdirected. Vaquita face extinction because of bycatch, not because of the lack of river flow.

An Economic Perspective on Policies to Save the Vaquita: Conservation Actions, Wildlife Trafficking, and the Structure of Incentives

“…As with many small cetaceans around the world, gillnets present the greatest threat to vaquita survival (Rojas-Bracho and Taylor, 1999;Rojas-Bracho and Reeves, 2013;Brusca et al, 2017;Brownell et al, 2019;Flessa et al, 2019). Gillnets set for totoaba pose the greatest risk to vaquitas due to the intensity of fishing, overlap with core vaquita habitat, and fishing practices with large mesh size nets.…”

Channel incision by headcut migration: Reconnection of the Colorado River to its estuary and the Gulf of California during the floods of 1979–1988

“…MacDougal and Sykes next ascended the Hardy. The tides were building towards the new moon spring on April 4, 1905 (Espenak, 2015) providing periodic slack periods resulting from fluvial/tidal counter pressure, but 3 days of lining/rowing were still required to ascend 30 km to the Sierra El Mayor. As they approached the mountains "heavy flow was noticed … although merely as a general surface movement and without any especial channel concentration which could be identified, round the southern extremity of the Cocopa [Sierra El Mayor] Mountains and undoubtedly working towards the Macuata [Laguna Salada] Basin upon the western side of the range" (Sykes, 1937a).…”

“…A related issue raised by Brusca et al (2017) concerns the current and past effects of the river's flow on the environment of the Upper Gulf and the endangered vaquita ( Phoecena sinus ), the Gulf of California Harbour Porpoise: see Lau and Jacobs (2017), Brusca (2018), Jacobs and Lau (2018) and Flessa et al (2019). This controversy and others concerning the significance of Colorado River discharge for Gulf of California productivity are beyond the scope of this review.…”