Linking Antarctic krill larval supply and recruitment along the Antarctic Peninsula.

Antarctic krill (Euphausia superba) larval production and overwinter survival drive recruitment variability, which in turn determines abundance trends. The Antarctic Peninsula has been described as a recruitment hot spot and as a potentially important source region for larval and juvenile krill dispersal. However, there has been no analysis to spatially resolve regional-scale krill population dynamics across life stages. We assessed spatiotemporal patterns in krill demography using two decades of austral summer data collected along the North and West Antarctic Peninsula since 1993. We identified persistent spatial segregation in the summer distribution of euphausiid larvae (E. superba plus other species), which were concentrated in oceanic waters along the continental slope, and E. superba recruits, which were concentrated in shelf and coastal waters. Mature females of E. superba were more abundant over the continental shelf than the slope or coast. Euphausiid larval abundance was relatively localized and weakly correlated between the North and West Antarctic Peninsula, while E. superba recruitment was generally synchronized throughout the entire region. Euphausiid larval abundance along the West Antarctic Peninsula slope explained E. superba recruitment in shelf and coastal waters the next year. Given the localized nature of krill productivity, it is critical to evaluate the connectivity between upstream and downstream areas of the Antarctic Peninsula and beyond. Krill fishery catch distributions and population projections in the context of a changing climate should account for ontogenetic habitat partitioning, regional population connectivity, and highly variable recruitment.