Abstract
Indo-Pacific lionfish were recently recorded in Veracruz Reef System (SAV) an ecosystem in the southwest of the Gulf of Mexico, which harbours endemic fish. The impact of lionfish over the reef fish community and over the trophic web of the SAV is unknown to date. This aimed to document the changes that occurred in the reef fish community after the arrival of lionfish in the ecosystem, mainly among endemic fish species, and the affected functional groups that make up the food web of the SAV. We analyzed the SAV monitoring database, obtained from surveys carried out annually since 2006, which included the density of the reef fish community and lionfish. A cyclical pattern was found in the reef fish community with a duration of four years. Since establishment of lionfish, the pattern has changed. There was a strong relationship between the densities of reef fish and of lionfish, suggesting that lionfish might be lengthening the recovery periods of the reef fish density. The diet was characterised through the inspection of 103 lionfish. The prey species with the highest relative importance index was Halichoeres burekae, one of the five endemic fish species of the region. Finally, an existing ECOPATH was modified to include lionfish. Endemic species were analyzed as independent functional groups, and their responses to create different scenarios of lionfish abundance were simulated. The analysis concluded that one of the functional groups positively affected by the lionfish invasion were echinoderms, among them the ecologically important Diadema urchin, while the functional group most detrimentally affected was the large groupers, which compete with lionfish for food.