Relative abundance distribution and body size changes of two co-occurring octopus species, Octopus americanus and Octopus maya, in a tropical upwelling area (south-eastern Gulf of Mexico)

Production of octopus fisheries is highly variable typically due to their sensitivity to environmental conditions. Using data from four scientific research cruises conducted in 2016 and 2017, we studied the influence of the environment on the relative abundance and distribution of two co-occurring octopus species, Octopus americanus (merobenthic) and O. maya (holobenthic), at the eastern part of the continental shelf of the Campeche Bank, a tropical upwelling area. By means of fitting hierarchical Bayesian spatio-temporal models, we found that the relative abundance of both species decreased with depth and when salinity and temperature were higher. The residual spatial distribution showed that variability in space for both species differed between seasons. In summer, when upwelling conditions dominate, O. americanus was abundant at the eastern part of the continental shelf, while O. maya dominated in the north-east and the coastal zone of Yucatan. In winter, when mixing conditions characterize the water column, O. americanus was abundant in coastal waters of Quintana Roo towards the north-west, whereas O. maya occurred mostly to the north-east. Additionally, the body weight of O. americanus decreased with depth, rocky bottoms and winter, while O. maya was smaller in shallower waters, sandy bottoms and summer. Overall, both species showed greater affinity for less saline and cooler waters, indicative of upwelling conditions. The spatial distribution differed between species and between sizes. We suggest that the ontogenetic differences would be associated with their distinct dispersal capacity during their early stages that would be under the influence of the Loop Current.