Population dynamics of the nonnative damselfish Neopomacentrus cyanomos and its potential competitors on coral reefs in the southern Gulf of Mexico

Abstract

Introductions of nonnative species are known to negatively impact coral reef ecosystems. The planktivorous Indo-Pacific damselfish Neopomacentrus cyanomos has spread throughout the Gulf of Mexico (GoM) over the past decade. However, its population dynamics and potential adverse effects on native reef fish communities have not been assessed. Here, we examined temporal changes in the occurrence, density, and social-group size of N. cyanomos on reefs in the southern GoM and assessed its possible impact on native species by (i) modeling the occurrence and densities of N. cyanomos and syntopic native fish species and (ii) evaluating differences in the species composition of the broader reef fish community on the Veracruz reef system (PNSAV) before and after N. cyanomos established there. Neopomacentrus cyanomos became more widely dispersed and abundant on PNSAV reefs from 2014 to 2021. Between 2006 and 2013 seven native fishes (four planktivores and three nonplanktivores) on PNSAV reefs experienced varying population trends. However, from 2014 onwards, populations of those seven species declined, although the 162-species PNSAV reef fish community did not exhibit notable shifts in species composition. Our results indicate that while N. cyanomos has become an increasingly common inhabitant of reefs in the southwestern GoM, it has had no measurable impact on native planktivorous fishes. Instead, changes in the populations of native species are likely related to the increasing habitat degradation of reefs immediately adjacent to a large city experiencing expanding industrial development. Detailed and mechanistic explorations are required to determine if N. cyanomos has negative ecological effects on wider Caribbean reefs.