This dataset is released under Open Government Licence, version 3.0 ().

We ask users of these data to kindly follow these guidelines:

1. Consult all appended files to avoid errors in interpretation. As for KRILLBASE-abundance, KRILLBASE-length frequency is a complex dataset comprising information from a wide variety of net sampling methods. Users are strongly urged to read this Discovery Metadata record and all files accompanying the LENGTH_DATA_20200201 file in order to screen the data appropriately to avoid erroneous conclusions being drawn.

2. Report any errors in the data to the Polar Data Centre at British Antarctic Survey polardatacentre@bas.ac.uk. This will allow us to log these changes and incorporate them into the next version.

3. To cite the data appropriately in any publications by means of its DOI.

Methodology:

The sampling information of each component haul is provided in the file named HAUL_METADATA_20200201. This file contains all the net sampling information (for example, net type, sampling depth, when and where the net haul was taken, environmental information etc). In this file, each row refers to a single sampling event (such as a single net haul). This is identified by the unique character string in its 'REF' column. The file README_HAUL_METADATA gives a complete description of each column of the HAUL_METADATA_20200201 file, and needs to be consulted before the data are used.

The file entitled LENGTH_DATA_20200201 contains all the individual measurements of the krill (length, sex and maturity stage, where available) and in this file each row represents one individual krill measured. The file README_LENGTH_DATA provides a description of each column of the LENGTH_DATA_20200201 file. The information in the metadata table and the length table can be linked using the 'REF' column.

The file NET_CODES_20200201 describes the nets in more detail and NET_TRAJECTORY_20200201 describes the types of net haul.

The figure in the file KRILLBASE_LF_DISTRIBUTION describes the circumpolar distribution of records.

Data collection:

Details of nets used are described in the file NET_CODES_20200201, types of net hauls are listed in the file NET_TRAJECTORY_20200201.

Data quality:

Please note that in some of the net hauls, the sampling information is incomplete. All blank fields are absent data, not zeros. In plotting the data against GEBCO bathymetry to determine water depth, it was found that a handful of stations plotted on ice shelves or on land. Water depths for these have been left blank. These may represent rounding errors for positions or incorrect latitudes and longitudes. We transcribed data as they were given to us, accepting the possibility of mistakes or rounding errors in the data. Users of the data are requested to check metadata and all associated files.