Decimation of a population of the endangered species Scutellastra mexicana (Broderip and Sowerby, 1829) (Mollusca, Gastropoda) in the Marias Island (Eastern Ocean Pacific) Biosphere Reserve

Scutellastra mexicana is the largest known patellid limpet species and probably is one of the most endangered marine invertebrates. The species was once distributed along the American Pacific coast from Mexico to Peru, but their large size (up to 35 cm long) and easy accessibility (shallow sublittoral), made it very vulnerable to human collection and now is extinct on most of the mainland Mexican coast. In August 2017, a large population of this species was found on Maria Cleofas island, off the coast of west-central Mexico (Marias Archipelago, Pacific Ocean). This constitutes the only report of a population of this species since 1988. A total of 808 adult individuals of up to 26 cm in length and 20 cm in width were estimated, together with the presence of juveniles, suggesting that it is a self-sustaining population. The population was monitored in August 2017 and August 2018. Although the species is under the category 'Special Protection' in the General Mexican Wild Law, and that Maria Cleofas island is a Biosphere Reserve, fishermen that operate with impunity in the area decimated the limpet population within a year of its discovery. Abundance in the shallowest area decreased significantly from 120 individuals per transect (65 m long and 2.75 m wide) in August 2017 to 48 individuals in August 2018, and the estimated adult population decreased from 808 to 304 limpets. Neither passive national conservation policies nor local practices have reduced current threats to biodiversity and resource depletion in Marias Archipelago. Protected areas like this are 'paper parks'-parks in name only-because there is no active conservation strategy or protection of marine species.