Acoustic instruments
Two SIMRAD scientific echo sounders, EK 400/38 kHz and EK 400/120 kHz were used during the survey for estimation of fish density. The EK 400/38 was coupled to a digital integrator QD as well as to an analog integrator QM. The details of the instrument settings used are as follows:
|
|
EK 400/38 |
EK 400/120 |
|
Range |
0-100 m or 0-250 m |
0-100 m |
|
Transmitter |
High (5000 W Nom) |
High (1250 W Nom) |
|
Bandwith |
3.3 kHz |
3.3 kHz |
|
Pulselength |
1.0 ms |
1.0 ms |
|
TVG |
20 log R |
20 log R |
|
Attenuator |
20 dB |
0 |
|
Rec. gain |
8 or 9 |
5 |
|
Transducer |
split beam (ES) |
Ceramic 10 cm |
QM settings: Gain 20 dB x 10. Threshold 7
A calibration experiment using standard copper spheres performened in Baia dos Tigres 26/4/89 gave the following results: 30x30 transducer, SL+VR: 141.46 dB, instr. constants 1 ms: 1.18, 0.5 ms: 2.30. ES transducer: SL+VR: 135.47 dB, instr. constant: 3.69. The result of the calibration showed that the 30x30 transducer was in-stable and hence the split beam transducer was used for integration.
Hydrography
Temperature, salinity and oxygen were 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 a thermograph.
Fishing gear
Bottom trawl: High opening shrimp and fish trawl with net headline 31m (floatline), footrope 47m, gear with 12 cm diameter roller disks, 40 m sweeps, estimated headline hight 6 m and distance between wings during towing 18-20 m.
Pelagic trawl: Type "Harstadtrawl", width about 30 m, vertical opening 10-15m.
Cod ends of trawls with fine meshed inner lining.
Figures giving details of the trawls are attached.
