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 (8×8)	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 (+3.3 dB to comp. for use of split beam transd.)
QM settings:	Gain 20 dB × 10, threshold 10
	Gain 10 dB × 10, threshold 1

A split beam echosounder ES-400 was coupled parallel to the EK-400/38 KHz to monitor and Log the TS distributions of the acoustic targets.

Sonar:

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

Calibration on standard target 8/11-85:

EK 400/38: SL + VR =	137.3 dB (Cu 60) with split beam transd.
	140.8 dB (Cu 60) normal 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 were sampled at standard depths with Nansen bottles. Oxygen was measured with the Winkler method and salinity determined with an inductive salinometer. Surface water temperature was recorded at 4 m depth with a 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 10-15 m; type modified “Bastrawl”, width abt 25 m, vertical opening abt 25 m; all trawls with fine-meshed inner lining in cod ends.

Constants applied for the bottom trawl survey:

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