Exploring the emergent niche of Greater argentine (Argentina silus) along gradients of topography, light and advection.

The World Ocean's midwater ecosystems are the largest habitat of the planet harbouring abundant and diverse micronekton communities, including the vast majority of Earth's vertebrates namely meso- and bathypelagic fishes. One fundamental ecological question is what facilitates diversification and different life-history strategies to evolve in this seemingly featureless seascape. Here we research the case of Greater argentine (Argentina silus) a little studied, but already commercially fished midwater species of the North Atlantic. We use a behavioural model, linking physics and biology through explicit mechanism of prey encounter and bioenergetics to make testable predictions that we confront with observation from the field. Advancing models and observations in lockstep allows us to enter a modelling-observation-modelling feedback loop where we use field data as it becomes available to refine model parameters and resulting predictions. We find, that a benthopelagic niche for Greater argentine emerges where the bottom topography blocks downward migrating micronekton from reaching safe and dark waters at greater depth. By varying environmental drivers, predator abundance, prey types, and advection in the model, we explore niche variability and consequences for stock productivity.