Are there distribution patterns and population structure differences among demersal fish species in relation to Antarctic benthic communities? A case study in the Weddell Sea

Despite the general belief that the Southern Ocean harbors low fish biodiversity, the Weddell Sea hosts one of the richest fish communities in the region. Parallelly, the Weddell Sea is also known for the presence of dense and diverse macrobenthos. Most macrobenthic invertebrates, such as gorgonians, sponges and bryozoans, are considered ecosystem engineers as they generate a three-dimensional structure that increases habitat heterogeneity. This structural complexity serves as a refuge against predators as well as a nursery ground for many organisms, including fish species. By analyzing video transects recorded by a Remotely Operated Vehicle, we investigated density, spatial distribution and size-frequency of populations of the demersal fish species inhabiting macrobenthic communities in the southernmost part of the Weddell Sea. We also attempted to unveil whether there is any relationship between benthic and fish communities and substrate, as well as some fish behavioral patterns. The dominance of juveniles in the surveyed fish assemblages provides evidence that, at this life stage, some fish species appear to be positively associated with complex benthic communities conformed by bryozoans, sponges and gorgonians which are more common in sand matrix with sparse rocks substrates. Moreover, about 37% of all specimens recorded were resting on benthic invertebrates or were using them to hide, implying that Antarctic benthic communities might offer suitable habitat. As such, it can be concluded that there was an apparent relationship between certain species of fish and the different benthic communities, yet the exact triggers and/or factors behind such an association remain partially elusive.