DOI: 10.5285/dfbcbbf9-8673-4fef-913f-64ea7942d97a
title: KRILLBASE-length frequency database, a compilation of scientific net sampling data on length, sex and maturity stage of Euphausia superba around the Southern Ocean, 1926 to 2016

description: The KRILLBASE-length frequency database comprises individual length measurements of 613487 Euphausia superba from 6470 scientific net hauls. Some of these individually-measured krill have additional information on their sex and maturity stage. Most of these E. superba are postlarvae, but some of the hauls include small (&lt; 20 mm) krill which likely include furcilia larvae as well as juveniles. Much of these data were compiled at British Antarctic Survey in 2007 by Mark Jessopp, with additional compilation by Angus Atkinson, Catherine Brewster and Natalie Ensor, and later data checking by Angus Atkinson with Helen Peat. The circumpolar distribution of records is illustrated in the file KRILLBASE_LF_DISTRIBUTION that is available along with this dataset. Examples of uses of KRILLBASE-length frequency are in Atkinson et al. (2009), Tarling et al. (2016), Perry et al. (2019) and Atkinson et al. (2019). The KRILLBASE-length frequency records were provided by contributing authors of the database or transcribed from the literature or from other institutional databases. At the time of data compilation, data from commercial-size large mesh trawls and from the commercial fishery was also transcribed, providing valuable information on the larger krill caught by these nets. These data are not included in this current KRILLBASE-length frequency database version, because of the difficulty in comparing them with the finer mesh scientific nets compiled here, and because length and population structure are also available in more complete form from CCAMLR. The KRILLBASE-length frequency database forms a complementary database to the KRILLBASE-abundance database (doi:10.5285/8b00a915-94e3-4a04-a903-dd4956346439), which compiles the abundance of Euphausia superba and salps in the Southern Ocean (Atkinson et al 2017). Both databases are multi-national, circumpolar compilations of net samples spanning years 1926 to 2016. The KRILLBASE-length frequency database uses some of the stations as KRILLBASE-abundance but also additional ones from targeted hauls or horizontal hauls.
description: 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.
description: Details of nets used are described in the file NET_CODES_20200201, types of net hauls are listed in the file NET_TRAJECTORY_20200201.
description: 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.