Environmental variables influencing the abundance of frog crabs (Brachyura Raninoidea) of the southwest Gulf of Mexico

Due to anthropogenic pressures, the global loss of biodiversity has increased the interest in understanding the relationship between species and their environment. However, there is still a gap in knowing this relationship for most species, more evident in small non-commercial species. The present study is the first specific effort to document the environmental variables influencing the abundance of rare frog crab species (Superfamily Raninoidea) in the continental shelf of the southwest Gulf of Mexico. The relative abundance of frog crabs, depth, bottom water (water salinity, water temperature, and dissolved oxygen), and sediment (calcium carbonate, organic matter, total organic carbon, and texture) were determined in 143 sampling sites during four research cruises conducted from 2012 to 2015. Five hundred and fourteen frog crabs were collected (90% in the Campeche Sound), belonging to Lysirude nitidus (A. Milne-edwards, 1880), Raninoides laevis (Latreille, 1825), R. lamarcki A. Milne-edwards and bouvier, 1923, and R. louisianensis Rathbun, 1933. R. louisianensis was the most abundant (441 individuals) and frequent species (collected in 37 sites). A Multivariate Generalized Linear Model (GLM) – using a negative binomial regression model - was performed to assess which environmental variables best explain the abundance of frog crab species. The GLM results showed that depth, salinity, temperature, and sand content in sediment were the most explanatory variables influencing the abundance of the frog crab species. R. louisianensis was significantly related with salinity and depth-salinity-sand interactions, R. lamarcki with depth-temperature and depth-salinity interactions, L. nitidus with depth, and R. laevis with temperature. These results suggest that spatial environmental variability in the southwest Gulf of Mexico (mainly related to the depth) influenced distinctly the abundance of each studied raninoid species promoting interspecific spatial segregation. Environmental optimal range, tolerance range, and tolerance limits are provided for each species, representing important baseline references for ecosystem and resources management. Regional terms: Atlantic Ocean, Gulf of Mexico, Mexico.