Ecoregionalization of myctophid fish in the Indian sector of the Southern Ocean: Results from generalized dissimilarity models

The Southern Ocean is delimited by major frontal zones which influence pelagic life at the spatial macroscale. There is a sharp ecological segregation of pelagic fish that inhabit this ocean with some families living in the neritic zone and others in the oceanic zone. The neritic zone is dominated by fish of the Notothenioid suborder. In the oceanic zone, mesopelagic species are dominated by myctophids. Their spatial distribution is highly influenced by meso- or sub-mesoscale oceanographic features. Myctophid presence/absence records from historical surveys and from the Census of Antarctic Marine Life were used to model species assemblages in the Indian sector of the Southern Ocean by using generalized dissimilarity modeling. This statistical technique is data-driven and is used in conjunction with Geographic Information Systems for creating models between communities and environmental factors. Application of these models in large unsurveyed areas is possible and helps in delineating regions of potential similar assemblages. This will allow us to move from the bioregionalization of the Southern Ocean based on only abiotic factors and chlorophyll, to its ecoregionalization by adding species assemblages.