Density-driven habitat use differences across fishing zones by predator fishes (Serranidae) in south-western Mediterranean rocky reefs

Abstract

The characterization of habitat use by predator species is crucial to understand its effect over fish distribution. We tested the hypothesis that fish density affects habitat use as well as influence on the relationships between top predators (groupers) and meso-predators (combers) by evaluating their distribution in and outside a marine reserve (MR) in SW Mediterranean Sea. All groupers showed significant higher densities inside MR. All species but Epinephelus costae (grouper) displayed a distinct microhabitat use between high- and low-density locations. When density is reduced, groupers occupied previously rejected microhabitats (shallow habitats) at MR, indicating the density-related distribution. Combers were negatively correlated and showed an opposite microhabitat-depth use demonstrating niche segregation. Groupers overlapped their spatial niche and were positively correlated probably due to food partitioning. We suggest the existence of cascading top-down effects on Serranus scriba (comber) population, at MR, reinforcing the importance of the protected areas for the recovery of top-predator populations and their key role on healthy ecosystem.