Tow krill raw counts and species abundance collected from the R/V Thuwal cruise in the Red Sea during January 2014

Data Type: Cruise Results
Version: 3
Version Date: 2022-05-26

» Red Sea Krill (Red Sea Krill)
Wiebe, Peter H.Woods Hole Oceanographic Institution (WHOI)Principal Investigator
Copley, NancyWoods Hole Oceanographic Institution (WHOI BCO-DMO)BCO-DMO Data Manager

Tow krill raw counts and species abundance collected from the R/V Thuwal cruise in the Red Sea during January 2014.


Spatial Extent: N:22.5293 E:39.0403 S:22.4209 W:39.0203
Temporal Extent: 2014-01

Dataset Description

Krill species raw counts and abundance per 1000 cubic meters are reported.

Acquisition Description

Three day trips were made aboard the R/V Thuwal to a location referred to as the Economic City Deep or ECDEEP: a ~700 m deep basin located north of KAUST at 22.5o N, 39.03o E).  A 1/4-m MOCNESS (Multiple Opening/Closing Net and Environmental Sensing System; Wiebe et al., 1985) with 200 µm mesh nets was used to sample the zooplankton.

Field sampling: The MOCNESS was obliquely towed four times from the stern A-frame using 11.43 mm conducting cable to 600 m depth with a ship speed nominally of 2 kts (Fig. 2; Table 1). Two MOCNESS tows were taken during daytime, one each on 7 and 8 January 2014, and two night tows were taken on 12 January 2014. The first day tow (m-25-001) was equipped with 5 nets that sampled 600-400, 400-200, 200-100, and 100-0 m. The second day tow (m-25-002) and the two night tows (m-25-003, m-25-004) each had six nets that sampled 600-400, 400-200, 200-100, 100-50, and 50-0 m. The first tow was done without having GPS data input to the MOCNESS acquisition program, so positions from the bridge were obtained for the tow start and end, and at each opening of a net. GPS positions were logged for the other three tows. The MOCNESS system was equipped with the standard SeaBird temperature and conductivity probes. Volume of water filtered by each net was based on the net frame angle and flowmeter counts using equation 10b in Wiebe et al., 1985.

The samples from the first tow were all preserved in 95% alcohol suitable for genetic analysis. Those from the other three tows were first split in a Folsom splitter (McEwen et al., 1954) and then one half was preserved in alcohol and the other half preserved in formalin. In the KAUST Red Sea Center laboratory, the euphausiids in the alcohol fraction of each of the stratified oblique samples were sorted using a dissecting stereomicroscope, identified using the Baker et al. (1990) guide, and counted.

The column "tow" in this dataset can be joined with the tow numbers in the dataset  'MOC_CTD_RedSea'

Processing Description

The counts of each euphausiid species for each net were standardized to the number of individuals/1000m3 for each depth stratum using the volume filtered by each net. The cumulative percent abundance (Baker, 1970; Pennak, 1943) was calculated starting from the bottom of each tow (i.e., the bottom of the first depth stratum where a species occurred was assigned 0 percent and the top of the final depth stratum of occurrence was assigned 100%). Depth (m) values of 25%, 50%, and 75% occurrence were interpolated based on the cumulative curve.

BCO-DMO Processing:

- added conventional header with dataset name, PI name, version date
- renamed parameters to BCO-DMO standard
- replaced space with underscore
- replaced blank cells with nd
- added activity, ISO_DateTime_Local columns
- changed cast type from MOC1 to MOC.25

2016-04-22: to enable joining: krill_by_sp and krill_by_tow: Changed instrument (was called cast_type) from MOC.25 to MOC-25 and changed tow from m_25_00# to #.

2016-05-04: created a new dataset by joining 'MOCNESS tow metadata' and earlier version of 'Krill abundance by tow', then manually added hypertext links to the appropriate tow physical data from 'MOC_CTD_RedSea'.

version 3. 2022-05-26:
Hyperlinks within the data table were removed and the linked dataset was instead added structurally as a "Related Dataset" to this Krill dataset page.  The hyperlinks were the corresponding tow data rows in the main data table of  'MOC_CTD_RedSea' .

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Related Datasets

Wiebe, P. H. (2015) MOCNESS CTD data from the R/V Thuwal cruise in the Red Sea during January 2014 (Red Sea Krill project). Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 2015-12-28) Version Date 2015-12-28 [view at BCO-DMO]
Relationship Description: Data from the same tow.

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cruise_idcruise identification unitless
yearyear yyyy
month_locallocal month mm
sitesite name unitless
depth_tow_maxmaximum depth of entire tow meters
insttype of gear: MOC.25 is a quarter-meter MOCNESS unitless
towMOCNESS tow number unitless
day_locallocal day dd
lat_startlatitude at start of tow; north is positive decimal degrees
lat_endlatitude at end of tow; north is positive decimal degrees
lon_startlongitude at end of tow; east is positive decimal degrees
lon_endlongitude at end of tow; east is positive decimal degrees
netnet number unitless
vol_filtvolume filtered cubic meters
stationsequential station unitless
yrday_local_startlocal year-day at start tow unitless
yrday_local_endlocal year-day at end tow unitless
depth_opendepth at which net was opened meters
depth_closedepth at which net was closeed meters
time_start_locallocal time at start of tow HHMM
time_end_locallocal time at end of tow HHMM
samp_fraction_denomdenominator of split fraction. e.g. for 1/2 split - samp_fraction_denom is 2 unitless
depth_intervaldepth strata sampled meters
depth_midmid-depth sampled by net meters
depth_maxmaximum depth sampled by net meters
E_diomedeae_cntEuphausia diomedeae raw counts number in split
E_sibogae_cntEuphausia sibogae raw counts number in split
E_sanzoi_cntEuphausia sanzoi raw counts number in split
S_affine_cntStylocheiron affine raw counts number in split
S_abbreviatum_cntStylocheiron abbreviatum raw counts number in split
E_diomedeae_1000m3Euphausia diomedeae abundance number/1000m^3
E_sibogae_1000m3Euphausia sibogae abundance number/1000m^3
E_sanzoi_1000m3Euphausia sanzoi abundance number/1000m^3
S_affine_1000m3Stylocheiron affine abundance number/1000m^3
S_abbreviatum_1000m3Stylocheiron abbreviatum abundance number/1000m^3

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Dataset-specific Instrument Name
MOCNESS-.25 m^2
Generic Instrument Name
Dataset-specific Description
This MOCNESS sampled with either 5 or 6 nets, 200 micron mesh.
Generic Instrument Description
The Multiple Opening/Closing Net and Environmental Sensing System or MOCNESS is a family of net systems based on the Tucker Trawl principle. The MOCNESS-1/4 carries nine 1/4-m2 nets usually of 64 micrometer mesh and is used to sample the larger micro-zooplankton.

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R/V Thuwal
Start Date
End Date
Three day trips to sample krill at ECDEEP station near Economic City, Saudi Arabia, north of KAUST.

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Project Information

Red Sea Krill (Red Sea Krill)

Coverage: Red Sea

The krill population at station ECDEEP was characterized via MOCNESS sampling and CTD casts.

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Funding SourceAward
King Abdullah University of Science and Technology (KAUST)

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