Habitat selection of high trophic-level predatory fishes in protected and unprotected areas: The effects of density and maturity stage

Abstract

Marine Protected Areas (MPAs) are useful tools for the conservation of fishes, providing that they include the essential habitats for the focal species. Habitat selection may depend on external (i.e., environmental conditions, food availability, and shelter) and internal (i.e., density-dependent processes) factors. Additionally, most fishes undergo ontogenetic shifts along their life cycles, thus, understanding the habitat requirements at each stage is of great interest for the correct design and functioning of MPAs. Here, we evaluated habitat preferences of high-level predatory fishes, namely Epinephelus marginatus, Epinephelus costae, Mycteroperca rubra, Dentex dentex, Sciaena umbra and Sphyraena viridensis to assess differences between species, maturity stages and density of fish. To do so, we applied Species Distribution Models (SDMs) in protected and unprotected areas along the coast of Murcia (SE Spain) to determine if those areas are properly located for the conservation of the focal species. We included three areas with different density of fishes. One area with high density in the long-term protected Cabo de Palos-Islas Hormigas MPA, and two with low density in the newly established Cabo Tiñoso MPA and the unprotected area of Cabo Cope. We evaluated the environmental variables that affect the occurrence of the species at two life stages, before and after achieving size at maturity. SDMs showed that bathymetry, habitat complexity and rocky bottoms were the most important drivers determining species distribution in both areas with high and low density of fish, although there were differences in the contribution of the variables at each location. Additionally, we found that habitat requirements were different for the immature and mature individuals, generally being the immatures the most sensitive to changes in habitats. Both MPAs and the unprotected area largely included areas of high suitability for the studied species, indicating that the MPAs are established in proper areas, and suggesting another area for the establishment of a new MPA to enhance a MPA network in the region.