Reef fish assemblages on Acropora patches in the Colombian Caribbean: resistance to reef degradation

Coral reefs are crucial habitats for many fish species because they serve as feeding and shelter sites. However, due to their sensitivity to environmental changes, reef degradation has led to a drastic decline in fish and reef assemblages, which has also been reflected in associated economic activities. The loss of branching corals Acropora palmata and A. cervicornis has reached up to 90% in the Colombian Caribbean, resulting in a reduction in the abundance and diversity of associated fish populations. During two time periods (2011–2012 and 2023–2024) across the Colombian Caribbean, fish associated with Acropora formations were evaluated in relation to patch size and health status of these coral species. The best conserved patches of A. palmata were found in the Tayrona National Natural Park (TNNP) and of A. cervicornis in the reefs of the Urabá Gulf. A total of 113 fish species from 34 families were associated with A. palmata , with the most represented families being Labridae, Haemulidae, Pomacentridae, and Serranidae. Acanthurus coeruleus, A. tractus, Chaetodon ocellatus, Haemulon flavolineatum, Scarus iseri , Sparisoma viride , Thalassoma bifasciatum, Abudefduf saxatilis , Microspathodon chrysurus , Stegastes adustus , and Canthigaster rostrata were the species common to all reef locations. In A. cervicornis formations, 78 species belonging to 25 families were recorded, with Labridae and Pomacentridae as the most abundant. Stegastes planifrons , Cephalopholis cruentata, and Hypoplectrus puella were the species common to all locations. The highest number of fish species was found in the TNNP (85 for A. palmata , 55 for A. cervicornis ). Although the status is critical throughout the Caribbean, further aggravated by the 2023–2024 bleaching event which caused A. palmata formations to practically disappear from two localities, this structural loss has not yet been reflected in the associated ichthyofauna. These results suggest that the fish assemblages linked to Acropora corals in the Colombian Caribbean remain relatively stable; however, it is unclear for how long they will persist.