INSTRUMENTS AND FISHING GEAR USED
Acoustic instruments
Two SIMRAD echo sounders EK 400, 38 and 120 kHz were used during the survey for estimation of fish density.
|
Instrument settings: |
|
|
|
|
|
|
|
|
EK400/38 |
EK 400/120 |
|
|
|
|
|
Range |
0- 100 |
0-400 or 0-200 |
|
Transmitter |
High(5000 W nom.) |
High (1250 Wnom) |
|
Bandwidth |
3,3 kHz |
3,3 kHz |
|
Pulse length |
1 ms |
1 ms |
|
TVG |
20 log R |
20 log R |
|
Attenuator |
20 dB |
0 dB |
|
Recorder gain |
7 |
5 |
|
Transducer |
Ceramic (8° × 8°) |
Ceramic (10 cm circular) |
QD settings: Gain 30 dB. Treshold 25 mV.
QM settings: Gain 20 dB x 10, treshold 10.
EK 400/120 was coupled to the other QM, Gain 10 dB x 10, threshold 0.
SONAR:
An ST-sonar was used to detect fish schools dose to the surface, Recorder range 0-250 m.
CALIBRATION ON STANDARD TARGET (Baia dos Tigres, 28.4 1985)
EK 400/38: SL + VR = 140,8 dB (Cu 60)
Hydrography
Temperature, salinity and oxygen content was sampled at standard depths with Nansen bottles. Oxygen was measured with the Winkler method and salinity determined with an 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, headline height during trawling abt 6 m, Pelagic trawls: Type “Harstadtrawl, width abt 30 m, vertical opening 14-16m; Type modified “Bastrawl”, width about 25 m vertical opening abt 25 m; all trawls with fine meshed inner lining in cod ens.
