Long-term environmental data explain better the abundance of the red octopus (Octopus maya) when testing the niche centroid hypothesis

Abstract

Correlative ecological niche models have been widely used to infer the organisms' environmental suitability; nevertheless, the relationship between this estimated suitability and their abundance is less clear. The ecological theory proposes that the internal structure of a species niche determines its abundance. Specifically, abundance should decrease from the niche centroid to its margins (i.e., distance to the niche centroid-abundance hypothesis - DNC-abundance), showing a negative relationship. This study tested this hypothesis using a high-quality dataset of catch per unit of effort as a proxy of the abundance of the red octopus (Octopus maya) collected during its fishing season in the Yucatan Shelf, Mexico in 2012. Species' niche was estimated with half of the abundance data taken as presence-only records and environmental variables that consisted of temperature and salinity. The remaining data were used to analyze the DNC-abundance. The protocol was repeated using the abundance and environmental data corresponding to each month of the fishing season. The effect of estimating the species niche was also examined using two different environmental datasets; one that matched abundance in a more finely temporal resolution (average values of the corresponding month in 2012 at a resolution of 9 km2) versus another one with a coarser temporal resolution (long-term data; salinity [1955–2006] and temperature [2002−2010] at a resolution of 1 km2). A consistent inverse relationship was found between abundance and distance to the centroid for the most evaluated scenarios, suggesting that niche structure could be informative for fishery monitoring even under climate change scenarios. In addition, contrary to our expectations, relationships were stronger when the coarse temporal resolution variables were used, which suggests that longer temporal envi- ronmental conditions may determine population abundance, probably due to seasonal aggregation in the western region of the Yucatan Peninsula.