Scientific echosounder data provide a predator’s view of Antarctic krill (Euphausia superba)

Brief description

Raw and processed acoustic data were collected in East Antarctica from the RSV Aurora Australis during two surveys: the Krill Availability, Community Trophodynamics and AMISOR Surveys (KACTAS) and the Krill Acoustics and Oceanography Survey (KAOS) in the East Antarctic.

Seabed alias example file used to make Figure 3.
38_false_bottom.sv.csv (file size: 10.7 MB)
This file is an example of seabed aliasing (false bottom echo) that occurred during the KAOS survey. The data in this file are acoustic (mean volume backscattering strength, Sv) sample-by-sample and in a CSV format.
Ping_index - ping number
Distance_GPS - along track distance from the vessel’s GPS (nautical miles).
Distance_vl - along track distance from the vessel’s log (nautical miles). Not used here, so is populated by Echoview’s ‘don’t care’ value (-9.90E+37) to keep the file format consistent.
Ping_date - format yyyy-mm-dd
Ping_time - format hh:mm:ss

Ping_milliseconds - format (integer; ms)
Latitude - position from the vessel’s GPS (degrees)
Longitude position from the vessel’s GPS (degrees)
Depth_start - start depth of vessel echosounder logging range (m)
Depth_stop - stop depth of vessel echosounder logging range (m)
Range_start - start range of vessel echosounder logging range (m)
Range_stop - stop range of vessel echosounder logging range (m)
Sample_count number of samples in a ping.
Acoustic Sv samples follow in column-wise vector (dB re 1 m-1)

Transect metadata
all_transects.csv (file size: 14.8 K)
This is the transect metadata for both the KACTAS and KAOS surveys:
Transect - transect number
startDate - start date of transect dd/mm/yyyy
startTime - start time of transect hh:mm
endDate - end date of transect dd/mm/yyyy
endTime - end time of transect dd/mm/yyyy
Ping_subset - a ping subset specified between two timestamps to isolate acoustic data that occurred on transect , i.e start timestamp to stop timestamp (yyyy-mm-dd hh:mm = yyyy-mm-dd hh:mm).
Direction - Direction traveled along the transect (N - north or S- south).
Light - day or night when transect was observed
Survey - Either KACTAS or KAOS
Leg - Krill box 1 or 2 (there were two surveys only during the KAOS voyage).
Pass - Sampling bout for a transect in a given direction.



Example R-code
FigureAndDataprocessingExample.R (12KB)
This R-code provides examples of scripting acoustic data processing using EchoviewR, specifically, using ping-subsets to isolate acoustic data along a transect of interest, detecting schools and exporting echo integrations for 38, 120 and 200 kHz. The R-code for making the figures in the paper is also given.

GPS vessel positions for both the KACTAS and KAOS surveys
KACTASandKAOS_GPS.csv (3 MB)
This CSV file gives the vessel track for both the KACTAS and KAOS surveys.
GPS_date - dd/mm/yyyy
GPS_time - HH:MM:SS
GPS_milliseconds - integer
Latitude - position from the vessel’s GPS (degrees)
Longitude - position from the vessel’s GPS (degrees)
x - relative grid position (x) used for plotting Figure 1
y - relative grid position (y) used for plotting Figure 1
Survey - either: KACTAS_Krillbox, KAOS_Krillbox1, or KACTAS_Krillbox2

Krill swarms for both the KACTAS and KAOS surveys
KACTASandKAOSswarms.csv (2.1 MB)
Krill swarms descriptors for the KACTAS and KAOS surveys in CSV format (see Table 2 for description of the data fields).

Echoview file for the KACTAS survey
KACTAS-survey.EV (21.8 MB)
An Echoview file (version 12.0) for the KACTAS acoustic data analysis

KACTAS EK60 scientific echosounder calibration values
KACTAS_EK500_calibration.ecs 3,623 16/05/2022 21:21 -a--
An Echoview format calibration file for the KACTAS survey (see Table 3 for calibration values and Demer et al.20 for a description of the calibration parameters).

Echoview file for the KAOS survey
KAOS-survey.EV (16.4MB)
An Echoview file (version 12.0) for the KAOS acoustic data analysis

KAOS EK60 scientific echosounder calibration values
KAOS_EK60_calibration.ecs 5,711 01/11/2021 04:36 -a–
An Echoview format calibration file for the KAOS survey (see Table 3 for calibration values and Demer et al. (2015) for a description of the calibration parameters).

Lineage

Progress Code: completed

Statement: 1. These active acoustic data are of a standard expected from data collected in the Southern Ocean. There are numerous examples of seabed aliasing ('false bottom') echoes found in the 38 kHz data collected during the KAOS survey. These echoes are expected from a high ping rate sampling over rapidly changing bathymetry and have been removed during data processing.

2. The volume estimates, and hence biomass estimates, of individual krill swarms should be used with caution: the volume estimates have been calculated assuming a cylindrical swarm shape, which is likely to underestimate swarm volume, so are best used as a relative measure.

Notes

Purpose
The two surveys, KACTAS and KAOS, were conducted to examine predator-prey relationships between air-breathing predators and Antarctic krill.