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Fish Acoustics Metadata
Revised August 30th 2007
Acoustics Equipment: Fish biomass was estimated throughout the water column with a BioSonics
DTX 120-kHz split-beam acoustics system (3 pings per second; 0.4 ms pulse length; -66 dB minimum
acoustic backscatter threshold). Its transducer was towed 1 to 2 m below the surface, depending
on sea state. Calibrations were conducted during every monthly cruise, using a 38-mm tungsten-carbide
calibration sphere.
Data Processing: Acoustic backscatter data (bs) were integrated using Echoview (SonarData Inc.,
Hobart, Tasmania), and exported in 50 m x 1 m bins. We used bs as a relative measure of fish biomass
density.
Variable Definitions
- Process ID: A number intended to be unique for each analysis export
on any one PC, which can be used to identify, retrospectively, the exported files which originated
from the same analysis.
- Interval: It reports the interval number of the cell being analyzed.
Each interval consists of ~50 m, either longitudinally or latitudinally.
- Layer: It reports the layer number of the cell being analyzed. Each layer consists of
1 m depth.
- Sv_mean: It reports the mean Sv in the domain which was analyzed (dB re 1m-1).
- NASC: It reports the Nautical area scattering coefficient for the domain
which was analyzed (m2/nmi2). Nautical area scattering coefficient is identical to sA as used by
Simrad and is the area backscattering coefficient (ABC) scaled by 4? and 1 nautical mile squared.
This terminology follows MacLennan and Fernandes (2000).
- Sv_max: It reports the maximum Sv in the domain which was analyzed (dB re 1m-1).
- Sv_min: It reports the minimum Sv in the domain which was analyzed (dB re 1m-1).
- Height_mean: It reports the mean height of the domain which was analyzed (m).
- Depth_mean: It reports the mean depth of the domain which was analyzed (m).
- Samples: It reports the number of good samples in the domain which was
analyzed. That is samples which are not in a visible bad data region or have a value of no_data.
- Layer_depth_min: It reports the minimum depth of the cell (layer) which was
analyzed (m). This is exported in depth mode only.
- Layer_depth_max: It reports the maximum depth of the cell (layer) which
was analyzed (m). This is exported in depth mode only.
- Ping_S: It reports the number of the first ping in the domain which was
analyzed (S for Start).
- Ping_E: It reports the number of the last ping in the domain which was
analyzed (E for End).
- Ping_M: It reports the number of the middle ping in the domain which
was analyzed (M for middle).
- Dist_S: It reports the distance (measured by GPS) from the first ping in
the analyzed variable to the first ping in the domain which was analyzed (S for Start).
- Dist_E: It reports the distance (measured by GPS) from the first ping
in the analyzed variable to the last ping in the domain which was analyzed (E for End).
- Dist_M: It reports the distance (measured by GPS) from the first ping in
the analyzed variable to the middle ping in the domain which was analyzed (M for Middle).
- VL_start: It reports the distance (measured by vessel log) from the first
ping in the analyzed variable to the first ping in the domain which was analyzed.
- VL_end: It reports the distance (measured by vessel log) from the first
ping in the analyzed variable to the last ping in the domain which was analyzed.
- VL_mid: It reports the distance (measured by vessel log) from the first
ping in the analyzed variable to the middle ping in the domain which was analyzed.
- Date_S: It reports the date of the first ping in the domain which
was analyzed (S for start).
- Date_E: It reports the date of the last ping in the domain which
was analyzed (E for end).
- Date_M: It reports the date of the middle ping in the domain which
was analyzed (M for middle).
- Time_S: It reports the time of the first ping in the domain which
was analyzed (S for start).
- Time_E: It reports the time of the last ping in the domain which
was analyzed (E for end).
- Time_M: It reports the time of the middle ping in the domain which
was analyzed (M for middle).
- Lat_S: It reports the latitude (in decimal degrees) of the first
ping in the domain which was analyzed (S for start).
- Lat_E: It reports the latitude (in decimal degrees)of the last ping
in the domain which was analyzed (E for end).
- Lat_M: It reports the latitude (in decimal degrees)of the middle ping
in the domain which was analyzed (M for middle).
- Lon_S: It reports the longitude (in decimal degrees) of the first ping
in the domain which was analyzed (S for start).
- Lon_E: It reports the longitude (in decimal degrees)of the last ping
in the domain which was analyzed (E for end).
- Lon_M: It reports the longitude (in decimal degrees)of the middle ping
in the domain which was analyzed (M for middle).
- Program_version: It reports the version number of Echoview used
for this analysis.
- Processing_date: It reports the date on which this analysis was conducted.
- Processing_time: It reports the time at which this analysis was conducted.
- EV_filename: It reports the name of the EV file from which this analysis was conducted.
- Alpha: It reports the value of Absorption coefficient entered on the Calibration
page of the Variable Properties dialog box for the variable which was analyzed (dB/m).
- ABC: It reports the Area backscattering coefficient for the domain which
was analyzed (m2/nmi2).
- Area_Backscatter_Strength: It reports the Area Backscatter Strength for the
domain which was analyzed (m2/nmi2). This is a logarithmic representation of ABC.
- Range_mean: It reports the mean range of the domain which was analyzed (m).
Contact Information:
Stuart A. Ludsin
Aquatic Ecology Laboratory, The Ohio State University
1314 Kinnear Road, Columbus, OH 43212
Phone: 614-292-1613
Email:
