the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 09 Jul 2026
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.
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Status: open (until 29 Oct 2026)
- RC1: 'Comment on essd-2026-450', Anonymous Referee #1, 28 Aug 2026 reply
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RC2: 'Comment on essd-2026-450', Anonymous Referee #2, 07 Oct 2026
reply
October 7, 2026
KRILLBASE-larvae: a database of abundance of eggs and larval stages of Euphausia superba in the Southern Ocean spanning 1926-2024
Author(s): Angus Atkinson et al.
MS No.: essd-2026-450
MS type: Data description article
Confidential comments to the ESSD editor
The KRILLBASE-larvae dataset is highly valuable and represents a long-awaited complement to the two previous datasets, KRILLBASE-abundance and KRILLBASE-length frequency. By compiling information on Antarctic krill eggs and larval stages, this manuscript has the potential to provide a useful baseline for future research on Antarctic krill biology, ecology, and fishery management.
I recommend major revisions before the manuscript can be accepted. My recommendation is based primarily on the need to improve precision, clarity, consistency, accessibility, and presentation rather than on concerns about the overall value of the dataset. The manuscript should define the temporal coverage accurately; describe the 43 database fields more clearly; explain the treatment of eggs, nauplii, metanauplii, calyptopis, and furcilia stages; justify the use of abundance per square metre (ind. m-2) rather than cubic metre (ind. m-3); simplify access to the database; and revise the figures, tables, author-contribution statement, and references to comply with journal standards.
I also suggest adding a new conceptual timeline showing the principal historical events that led to the collection of this 43-field dataset. Readers may find it informative to learn who conducted the pioneering work during the discovery era and how the modern era developed its focus on the eggs and larvae of Euphausia superba. Such a figure would help integrate the historical structure of the dataset and clarify the distinction between the discovery and modern sampling periods.
Detailed comments are provided in the attached PDF file to improve the manuscript’s clarity and presentation. I am convinced that, after careful revision for clarity, precision, and eloquence, the manuscript and dataset will constitute a valuable resource for the Antarctic krill research community.
Comments to the authors
The KRILLBASE-larvae dataset is a valuable contribution and a long-awaited complement to KRILLBASE-abundance and KRILLBASE-length frequency. The manuscript would benefit from major revisions to improve its precision, consistency, accessibility and presentation. My specific comments are provided below.
Title and temporal coverage
Should the dataset be named KRILLBASE-eggs-larvae? The dataset includes both eggs and larvae, not larvae alone. I recognise that this name is longer, but it would be more precise.
The Abstract should also mention that KRILLBASE-larvae is a database divided into two main periods, 1926–1937 and 1976–2024. Therefore, in the title, “1926–2024” should be replaced with “1926–1939 and 1976–2024” to provide precise information about the periods for which data are available. A longer but more elegant title could refer to a discovery era (1926–1939) and a modern era (1976–2024). Please note that Fig. 4 shows data up to 1939 rather than 1937. Check the data and correct this inconsistency accordingly.
I therefore suggest changing the title as follows:
KRILLBASE-eggs-larvae: a database of abundance of early life stages of Euphausia superba in the Southern Ocean during a discovery era (1926–1939) and a modern era (1976–2024)
In institutional address 7, please delete the number “11” between “7” and “Consejo”.
Abstract
The Abstract states: “key sampling information such as sampling depths, net type, net mesh size, water depth, temperature etc.” I think that net type should be mentioned first. The distinction between net sampling depth and water depth is also somewhat confusing. What is the difference between these two variables? Please correct this wording and provide a clearer explanation of the variables included in the database. I recommend that the authors describe all variables in the same order as the database columns. For example: “key sampling information such as net type, net mesh size, net sampling depth, seafloor depth and temperature”. Do not use “etc.”, because it is misleading. As a reader, I cannot determine whether the database contains two additional variables or twenty. If the list is too long to include in the Abstract, state how many variables the database contains and summarise their categories, such as sampling, krill and environmental variables. In short, describe precisely what the database includes rather than ending the description with “etc.”
Scientists tend to avoid the word “important” in scientific articles because it is subjective: the same subject may be important to some readers but not to others. It would be preferable to explain directly why this species is biologically, ecologically or otherwise relevant without repeatedly describing it as “important”.
The Abstract currently gives a webpage link, username and password for reviewers. I assume that this information will be changed if the manuscript is accepted and that instructions will be provided for members of the public to access this relevant database.
In Section 2.2, “KRILLBASE-larvae: relationships with other databases”, the manuscript states: “KRILLBASE-larvae provides numerical abundances (no. m−2 within the depth range sampled by the net) of eggs, nauplii, and individual calyptopis and furcilia stages”. Early ontogenetic development comprises specific stages and substages, and it is important to clarify whether the database includes or excludes them. If they are included, the sentence should read: “KRILLBASE-larvae provides numerical abundances (no. m−2 within the depth range sampled by the net) of eggs without differentiation by embryonic stage, two naupliar stages, one metanauplius stage, three individual calyptopis stages and six individual furcilia stages.”
As a krill biologist, I know that Euphausia superba has a metanauplius stage, but the dataset combines nauplii and metanauplii. Please explain why these life stages were combined.
Unfortunately, the repository link on the BAS website does not display a readily visible login button for entering a username and password, forcing users to read a separate instruction page to determine how to log in. After a considerable time, I discovered that the cogwheel icon in the upper-right corner, to the right of the search box and magnifying-glass icon, provides access to the login page. This option is quite hidden. It should be replaced, or at least accompanied, by a clearly visible button labelled “Login” on the main webpage. Please make the process for downloading this future open-access dataset easier.
Introduction
Again, please avoid repeatedly using the adjective “important”. Replace it with an explanation of why the relevant feature, process or species is important in each context.
After searching for a considerable time, I found the correct webpage: https://data.bas.ac.uk/full-record.php?id=GB/NERC/BAS/PDC/02221. From this page, I was able to download the KRILLBASE-larvae.csv dataset, an 8.6 MB file, without difficulty once I had located the correct record. In short, the present procedure for obtaining the dataset is too complicated, and I was not able to open the intended dataset easily.
I recommend stating explicitly whether the database excludes information on eggs by developmental stage, including the single-cell, multiple-cell, blastula, gastrula, early limb-bud, late limb-bud and twitching-embryo stages. The authors could cite any of the following references:
Quetin, L. B. & Ross, R. M. (1984). Depth distribution of developing Euphausia superba embryos, predicted from sinking rates. Marine Biology, 79(1), 47–53.
George, R. Y. & Strömberg, J. O. (1985). Development of eggs of Antarctic krill Euphausia superba in relation to pressure. Polar Biology, 4(3), 125–133.
Jia, Z., Virtue, P., Swadling, K. M. & Kawaguchi, S. (2014). A photographic documentation of the development of Antarctic krill (Euphausia superba) from egg to early juvenile. Polar Biology, 37(2), 165–179.
In the Abstract and Results sections, provide a summary of the entire KRILLBASE-larvae dataset. I suggest adding text such as the following:
Database description and access
This dataset contains 43 variables grouped into five main categories: 13 columns describing sampling location and time, 5 columns characterising sampling gear and effort, 3 columns representing environmental conditions, 18 columns reporting the abundance and occurrence of eggs and larval developmental stages, and 4 columns providing comments and quality-control information related to sampling and data entry (Table 2).
A potential classification of the variable types included in the KRILLBASE-larvae dataset is shown below.
Sampling location and time
1 FILE_SOURCE
2 REFERENCE
3 SHIP_AND_COUNTRY
4 RECORD_TYPE
5 STATION
6 LATITUDE_DEGR4EE_NORTH
7 LONGITUDE_DEGREE_EAST
8 SEASON
9 YEAR
10 MONTH
11 DAY
12 NET_TIME
13 DAY_NIGHT
Sampling gear and effort
14 NET_TYPE
15 MOUTH_AREA_OF_NET_M2
16 NET_MESH_SIZE_MICRONS
17 TOP_SAMPLING_DEPTH_M BOTTOM_SAMPLING_DEPTH_M
18 VOLUME_FILTERED_M3
Environmental conditions
19 MEASURED_SURFACE_TEMPERATURE_CEL
20 CLIMATOLOGICAL_ TEMPERATURE_CEL
21 WATER_DEPTH_WITHIN_10_KM_M
Abundance and occurrence of eggs and larval developmental stages
22 EGGS_UNDER_1M2
23 NAUPLII_PLUS_METAUPLII_UNDER_1M2
24 CALYPTOPE_1_UNDER_1M2
25 CALYPTOPE_2_UNDER_1M2
26 CALYPTOPE_3_UNDER_1M2
27 FURCILIA_1_UNDER_1M2
28 FURCILIA_2_UNDER_1M2
29 FURCILIA_3_UNDER_1M2
30 FURCILIA_4_UNDER_1M2
31 FURCILIA_5_UNDER_1M2
32 FURCILIA_6_UNDER_1M2
33 TOTAL_EGGS_NAUPLII_METANAUPLII_UNDER_1M2
34 TOTAL_CALYPTOPES_UNDER_1M2
35 TOTAL_FURCILIA_UNDER_1M2
36 TOTAL_CALYPTOPES_PLUS_FURCILIA_UNDER_1M2
37 NUMBER_OF_LARVAE<=10MM-UNDER_1M2
38 NUMBER_OF_LARVAE_11_TO_15MM_UNDER_1M2
39 PRESENCE_1_OR_ABSENCE_0_OF_CALYPTOPES_AND_FURCILIA
Additional comments
40 COMMENTS_ON_SAMPLING_STATIONS_NETS_DEPTHS
41 COMMENTS_ON_SAMPLING_DATES_AND_TIMES
42 COMMENTS_ON_DAY_NIGHT_ATTRIBUTION
43 COMMENTS_ON_DATA_ENTRY_FOR_LARVAL_STAGES
Why are all field names written in capital letters? Text in capitals is difficult to read. I suggest using an initial capital letter followed by lower-case letters to make the field names more reader-friendly.
In the Abstract, explain why the abundance of eggs and larvae is expressed per unit of surface area (m−2) rather than per unit of volume (m−3). I consider a volumetric measure to be more informative, but the authors may have a sound rationale for expressing abundance as ind. m−2.
Contribution authors
Abbreviation of three coauthors are not mentioned on contribution authors: Simeon Hill, Geraint Tarling, and Emma Cavan.
Figures
All figures and tables must be edited carefully to comply strictly with the journal’s format.
Figures 1, 3, 4 and 6: remove the outer frame. International journals do not generally use this unnecessary outer black line.
Figure 4 shows data up to 1938 and 1939, whereas the Abstract and main text state that the discovery-era data extend only to 1937. Please check this inconsistency and correct it throughout the manuscript.
Figure 5 contains many repeated x- and y-axis titles. Show each shared title only once and use a larger font. This will simplify the figure, improve clarity and save space, allowing each panel to be enlarged. Make all panels the same size and present them in black and grey rather than blue and red, because the latter colours are not sufficiently intuitive. I suggest placing all panels currently shown in blue in a horizontal upper row and all panels currently shown in red in a horizontal lower row. The upper and lower rows should have the same sampling range and share the same y-axis; the y-axis should be shown only on the left-hand panel of each row rather than repeated in every panel. Label the upper-row panels A, B, C and D, and the lower-row panels E, F, G and H.
Figure 6: all panels repeat the same x-axis values and x-axis title. Show these only on the lowest panel and remove the spaces between the vertically arranged panels. Add labels A, B and C, and preferably use black rather than blue bars.
For the y-axis, delete the titles from the upper and lower panels and retain only one centrally positioned title in a larger font. More generally, enlarge the axis numbers and titles so that they are proportional to the graphs and can be read easily.
Figures 7 and 8: all legends and scales are too small and are difficult to read. One alternative would be to place the scale below each graph and use a larger font.
An initial conceptual timeline of the historical events that made it possible to collect data on the eggs and larvae of Euphausia superba could be interesting. This is only a suggestion.
In the figure legend for panel (a), explain whether mean abundance combines eggs through furcilia, nauplii through furcilia, or only calyptopis through furcilia. It is not clear what is plotted as mean krill density. The same applies to panels (b) and (c); please specify which life stages are combined in each case.
In the Author contributions section, three co-authors are not mentioned as contributors: Simon Hill (SH), Geraint Tarling (GT) and Emma Cavan (EC). In addition, why is VS, whom I assume to be Volker Siegel, not listed as a co-author? Please spell out the name.
Tables must follow the journal’s editorial format and should avoid vertical and horizontal lines.
References
The references must be revised carefully to follow the journal’s editorial format. Many references still lack DOI links, and the formatting remains heterogeneous. I identified the DOI links up to Cavan et al.; the authors should locate and add the DOI links for the remaining references where available.
Overall recommendation
I recommend major revisions. The dataset is highly valuable, and the manuscript is likely to become a useful baseline for future research on Antarctic krill biology, ecology and fisheries management. Addressing the points above will substantially improve the clarity, precision, accessibility and overall presentation of the work.
Data sets
KRILLBASE-larvae: a database of abundance of eggs and larval stages of Euphausia superba in the Southern Ocean spanning 1926-2024 A. Atkinson et al. http://ramadda.data.bas.ac.uk/repository/entry/show?entryid=946546c8-b24f-422f-96e1-3bd872506c5f
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The manuscript titled “KRILLBASE-larvae: a database of abundance of eggs and larval stages of Euphausia superba in the Southern Ocean spanning 1926 – 2024” is well written and provided information on the records of krill larvae in the Southern Ocean. I consider this compilation as unique and as an excellent addition to the existing database KRILLBASE on postlarvae krill.