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 & digital integrator OD 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 or 0-250 |
0-100 |
|
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 |
5 |
|
transducer |
8 x 8 ceramic |
Ceramic 10 cm Æ |
|
|
Split beam (ES) |
|
QM settings: Gain 20 dB x 10. Threshold 7
A calibration experiment using standard copper spheres performed at Las Palmas 27/8/89 gave the following results: 30x30 transducer, SL+VR: 141.75 dB, instr. constants 1ms: 0.90, 0.5 ms : 2.10. ES transducer: SL+VR: 134.7 dB , instr. constant: 4.47.
Hydrography
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), foot-rope 47m, gear with 12 cm diameter roller disks, 40 m sweeps, estimated headline height 6m and distance between wings during towing. 18-20m.
Pelagic trawl: Type "Harstadtrawl", width about 30m, vertical opening 10 - .15m.
Cod ends of trawls with fine meshed inner lining.
Figures giving details, of the trawls are attached.
DESCRIPTION OF PELAGIC AND BOTTOM TRAWL.
