KRILLBASE-larvae: a database of abundance of eggs and larval stages of Euphausia superba in the Southern Ocean spanning 1926–2024

Abstract. Antarctic krill (Euphausia superba, hereafter "krill") are an important component of Southern Ocean food webs, are efficient in sequestering carbon and support a major fishery. Knowledge of their early life cycle is key to understanding krill population dynamics and essential for fisheries management in a warming climate. Many data have been collected over the years on the distribution of krill larvae, but the data remain fragmented and hard to re-use. Here we have put these disparate data sources together into a large database of 10,762 net-sampling records with numerical abundance data on the various larval stages. This new KRILLBASE-larvae database complements two existing and circumpolar KRILLBASE open-access databases, namely KRILLBASE-abundance (numerical abundance of postlarval krill and salps) and KRILLBASE-length frequency (length, sex and maturity stage of postlarval krill). By completing the set to include larvae, we provide datasets that can underpin a more holistic appreciation of krill dynamics; for example to model the krill life cycle, population dynamics, response to climate change and to help manage the krill fishery. KRILLBASE-larvae is circumpolar, albeit with most data concentrated in the SW Atlantic sector which appears to be the major spawning ground and where the fishery operates. The data span 1926–2024 with >50 seasons of coverage spanning two epochs: 1926–1937 and 1976–2024. The database is based on net haul data on densities (numbers per m^-2) of eggs, nauplii, metanauplii, calypotope- and furcilia stages, alongside key sampling information such as sampling depths, net type, net mesh size, water depth, temperature etc. This data paper provides a description of KRILLBASE-larvae, mapping data coverage in terms of space, time and sampling depth, providing pointers and caveats to its use. The KRILLBASE-larvae database is available here for reviewers: http://ramadda.data.bas.ac.uk/repository/entry/show?entryid=946546c8-b24f-422f-96e1-3bd872506c5f with user id reviewer_02221 and password VchJWSANpH1T5Wpj with instructions https://www.bas.ac.uk/data/polar-data-centre/reviewer-access/ [Pending publication and any subsequent amendment on review, the final dataset will be freely available with a doi and single click to download]. We request that this data doi and the data paper are cited when the data are used.