Acoustic instruments
SIMRAD sounders coupled to QM integrators were used for estimating fish density:
EK 38 KHz (1st and 2nd surveys): basic range 0-100 m + 100m; Transmitter Ext 2.5 Kw; Bandwidth and pulse length 3 KHz, 0.6 ms; TVG and GAIN 20 log R-20 dB; Recorder gain 7; Transducer ceramic 9×8 degr.square
QM integrator: Gain 20 dB × 10, Threshold 0.8
|
SL + VR = |
137.9 dB (Calibration 22 Nov 1982 on standard
sphere) |
|
|
137.9 dB (Calibration 4 Dec 1983) |
Bandwidth and pulse length 3.3 KHz, 1.0 ms; TVG 20 log R; Attenuator -20 dB;
Recorder gain 7; Transducer ceramic 9×8 degr. square
SL + VR 140.7 dB (Calibration 17 May 1984 on standard sphere)
QD integrator (3rd survey): Gain 30 dB, Threshold 17 mV.
EK 400/120 Khz: Basic range 0-100m; Transmitter High, Bandwidth and pulse length 3.3 KHz, 1.0 ms; TVG and GAIN 20 log R-0 dB
Recorder Gain 4; Transducer ceramic 10 degr. circular
QM integrator: Gain 10×10 Threshold 0
SL + VR = 112.2 dB (Calibration 31 Aug 1982 on standard sphere)
Hydrography
Temperature, salinity and oxygen content were sampled at standard depths with Nansen bottles. Oxygen was measured with Winkler method and salinity determined with inductive salinometer. Surface temperature was recorded at 4 m depth with thermograph.
Fishing gear
Bottom trawl: High opening shrimp and fish trawl with rubber bobbins gear.
Headline 31 m, assumed effective width 18.5 m; height during trawling abt 6 m.
Pelagic trawls: Type “Harstadtrawl”, meshsize codend 21 mm, width abt 30 m, vertical opening abt 15 m; Type modified “Krilltrawl” width abt 50 m, vertical opening abt 30 m, codend meshsize 9 mm.
