Human and conservation factors affect spatial variation of reef fish assemblages in Colombian Pacific reefs

Humans have both negative and positive impacts on marine communities: human everyday activities can degrade ecosystems, while conservation efforts can support their protection and recovery. Using an empirical database of fish assemblages compiled from 393 underwater visual censuses along the Colombian Pacific Coast, we assessed spatial variation in these assemblages and investigated whether they are shaped by human pressures, such as number of fishers and proximity to markets, as well as conservation measures, including protection status and the age of the marine protected areas. Our study reveals that remote locations have a higher fish density and biomass than those near the coast. We found that grunts (Haemulidae) were the most species-rich family and contributed the most to fish density and biomass. Piscivores were the trophic group most affected by human factors, showing lower species richness, density, and biomass in coastal locations. In contrast, other trophic groups did not show a negative response to human factors across locations. We did not observe an effect of human and conservation factors on the total species richness. To evaluate the potential influence of Malpelo island, the only oceanic location in the dataset, we built two models, one with and one without this site. The results were consistent across both models, indicating that including or excluding Malpelo did not alter overall patterns of species richness. However, market distance negatively influenced the average fish density and biomass when all locations were included. Our results provide the first quantitative assessment of fish assemblages across the Colombian Pacific Coast, enabling future comparison and enhancing our understanding of the effects of human and conservation activities on the patterns of species richness, density, and biomass of reef fishes in the Eastern Tropical Pacific.