Spatial distribution of Serranid fish in the Gulf of California, Mexico

The Gulf of California (GC) covers nine degrees of latitude and is a significant fishing area in Mexico. These fisheries are mostly small-scale where reef fish, particularly groupers (Serranidae), represent an important portion of it. In this family, eleven species are found in shallow waters: four species of Mycteroperca spp, two Cephalopholis spp, one Epinephelus spp, two Paralabrax spp, one Alphestes spp and one Serranus spp. Some of these species are particularly targeted (M.rosacea and Paralabrax spp) or were fished (M.jordani, M.xenarcha) when others are less caught (Cephalopholis spp, Epinephelus spp) or not targeted (Alphestes spp, Serranus spp). Despite the importance of serranids for resources and ecosystem functioning (top-predators), a large spatial study along the GC is still lacking. Here, we studied the spatial distribution pattern of serranids density and biomass in the GC using a large set of 14.000 scuba-diving transects of 160 reefs between 1998 and 2024. To understand the observed spatial pattern, we estimated the relationship with various environmental (shelf area, chlorophyll, isolation, depth) and anthropogenic (protection status, human population) factors. Serranids composition shows north-south spatial variation, with higher biomass and density of large species in the north in contrast to smaller species, which are more prevalent in the south. The northern part of the GC presents more temperate environment, with high primary productivity and lower human populations densities which can support the presence of larger species. These findings could help the implementation of conservation politics for these species.