Damage caused by crown-of-thorns starfish (Acanthaster cf. solaris) outbreak to restored corals in the southern Gulf of California, Mexico

In the last decades, managers and local communities have been turning to active restoration as a mechanism to recover damaged reefs affected at an unprecedented rate because of climate change, anthropogenic activities, and natural events, such as outbreaks of the crown-of-thorns starfish (COTS) Acanthaster spp. A coral restoration experiment was conducted in the southern Gulf of California (24°N, 110°W) starting in December 2017. By early 2018, unusually high numbers of Acanthaster cf. solaris appeared at the restoration plots causing significant coral mortality. Fragment survivorship was significantly influenced by site with corals at Roca Swan showing a longer survival probability time [297.43 (SE 16.38) d] compared to El Corralito [133.81 (SE 7.73) d]. From April 2018 to June 2019, average abundance of A. cf. solaris had surpassed 800 ind ha–1 at three sites, and their feeding resulted in high fragment mortality ranging from 39% at Roca Swan to 88% at El Corralito—a strong contrast to other restored reefs along the eastern Pacific where starfish were absent and annual fragment mortality was <15%. La Paz Bay was the first area in the eastern tropical Pacific to suffer an A. cf. solaris outbreak in 2017–2018, severely hindering success of coral restoration programs.