APPENDIX I: Instruments and fishing gear used

Acoustic instruments:

Two Simrad echosounders EK 400, 38 and 120 kHz were used during the survey for estimation of fish density.

Instrument settings:

	EK 400/38	EK 400/120
Range	0-100+100	0-100
Transmitter	High (5 kW nom.)	High (1.25 kW nom)
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	Split beam ceramic (8 x 8)	Ceramic (10 cm circ.)

EK 400/38 was coupled to the digital integrator QD and to analog integrator QM.

QD settings:	Gain 33.3 dB, Threshold 10 mV
QM settings:	Gain 20 dB × 10, threshold 10
	Gain 10 dB × 10, threshold 1

Sonar:

A ST - sonar was used to detect fish schools close to the surface. Recorder range 0-250m.

Calibration on standard target. 29/4-85:

EK 400/38 :	SL + VR = 137.3 dB (Cu 60) with split beam transd.
EK 400/120 :	SL + VR = 112.1 dB (Cu 30) (3/2 -85)

Instrument constant for biomass calculations : C = 0.094 m /mm/nm

Hydrographic equipment

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 4m depth with a thermograph.

Fishing gear

Bottom trawl: High opening shrimp and fish trawl with rubber bobbins gear, headline 31m, headline height during trawling abt 6m.

Pelagic trawls: Type "Harstadtrawl" , width abt 30 m, vertical opening 10 - 15 m; Type modified "Bastrawl", width abt 25m, vertical opening abt 25 m; all trawls with fine meshed inner lining in cod ends.

Contants applied for the bottom trawl survey;

Catchability coefficient	: Q = 1.0
Distance between wings of trawl during trawling	: 18.5 m