The development of a preliminary rock reef fish multimetric index for assessing thermal and urban impacts in a tropical bay

•We developed a multimetric index for assessing thermal and urban influence on fish community.•Metrics were selected based on structural/functional characteristics of the fish community.•This index succeeds in discriminating control/impacted sites by thermal and urban influences.•This preliminary multimetric index has potential to be used in tropical rock reef coastal areas.

We developed a multimetric index for assessing ecological conditions in rocky reefs areas to evaluate thermal and urban influences on fish community. Eight metrics were selected to assess thermal influence: (1) total number of species; (2) number of water column species; (3) number of transient species; (4) density of individuals with low resilience; (5) density of omnivores; (6) density of carnivores; (7) number of cryptic species; (8) density of herbivores. For urban influence, six metrics were selected: (1) total density; (2) ratio between the number of rare species and the total number of species; (3) density of individuals with heavy fishing pressure; (4) number of resident species; (5) number of cryptic species; (6) density of herbivores. This preliminary index succeed in discriminating control/impacted sites and proved to be an important tool to assess impacts that alter fish community and have potential to be used in tropical rock reef coastal areas.