Deep Sea diving /

The Islas Marias Expedition


The legendary Tres Marías Islands


In year 2010, my friends and colleagues Karina Santos del Prado, Margarita Caso, and Eduardo Peters, all in the Direction of Ecosystem Conservation at Mexico’s National Institute of Ecology, got in contact with me and Octavio Aburto to organize an oceanographic expedition to the Tres Marías Islands.

This beautiful group of islands is situated about seventy miles west of Nayarit, in the Mexican Pacific Ocean, in latitude 21° N and longitude 106° W. After being largely overlooked by explorers during the Spanish colony, they received two natural history expeditions in the late 1800s. The first one was done by Andrew J. Grayson, who explored the Socorro and Marías Islands with financial support from the Smithsonian Institution and the Boston Society of Natural History in three research trips (1865, 1866 and 1867). Sadly, Grayson died as a result of some undefined “fever” during his fourth expedition in 1969. His field notes were published posthumously in 1871.

The second expedition took place almost three decades later, in 1897, with funding from the US Biological Survey and full support from Don Matías Romero, the Mexican Ambassador in Washington. Led by the indefatigable explorer Edward W. Nelson, the results were published in 1899 by the Division of Biological Survey at the USDA. This book is, to this day, a fundamental reference and a historic baseline for these still largely unexplored islands.

Shortly after, in May 1905, the main island (María Madre) was turned into a prison by the government of Porfirio Díaz, and access to the archipelago became extremely limited for security reasons. Since then, publications on the natural history and the biology of the islands have been few and sporadic, based on the results of a few rare research expeditions exceptionally allowed by the authorities of the penal facility.

With the turn of the 21st Century in year 2000, and under a growing environmental awareness within the Mexican Government, the Archipelago was declared a protected Biosphere Reserve under Mexican legislation. Although the penal colony is still operating on the main island, all other three islands are now formally protected. Since their dedication as wilderness reserves, the National Institute of Ecology and the Commission for Protected Natural Areas have started a series of exciting research initiatives in these legendary and remote ecosystems.

Our expedition produced the first comprehensive report on the underwater biota of the archipelago. Here we present the taxonomic report, led by Brad Erisman and published as a research paper in the journal Zootaxa. I have also uploaded the scanned copies of the 19th Century natural descriptions by Andrew Grayson and Edward Nelson (both publications are in the public domain, and have been digitized by Google books).

We hope this compilation of information might useful for researchers working in this unique region of Mexico:

Erisman, B.E., G.R. Galland, I. Mascareñas, J. Moxley, H.J. Walker, O. Aburto-Oropeza, P.A. Hastings, and E. Ezcurra. 2011. List of coastal fishes of Islas Marías archipelago, Mexico, with comments on taxonomic composition, biogeography, and abundance.Zootaxa 2985: 26–40.

Grayson, Andrew J. 1871. On the Physical Geography and Natural History of the Islands of the Tres Marias and of Socorro, off the Western Coast of Mexico. From the Proceedings of the Boston Society of Natural History, Press of A. A. Kingman, Boston. 45 pp.

Nelson, E.W. 1899. Natural History of the Tres Marias Islands, Mexico. (series on North American Fauna No. 14, prepared under the direction of Dr. C. Hart Merriam). Division of Biological Survey, U. S. Department of Agriculture, Washington, D.C. 97 pp. 


Report of our 2010 expedition

Open publication - Free publishing - More islas marias


Col. Grayson's report, year 1868

Open publication - Free publishing - More islas marias


Edward Nelson's 1897 expedition report

Open publication - Free publishing - More exploration



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