INSTRUMENTS AND FISHING GEAR USED
Acoustic instruments
Simrad sounders coupled to QM integrators were used for estimating fish density:
EK 38 KHz: Basic range 0-100 m; Transmitter Ext. 2.5 kw; Bandwidth and pulse length 3 KHz, 0.6 ms; TVG and GAIN 20 log R - 20 dB; Recorder gain 7; Transducer ceramic 9x8 degr. square; QM integrator: Gain 20 dB x 10, Threshold 0.8 SL+VR = 137.4 dB (Calibration 11 Feb 1982 on standard sphere)
EK 120 KHz (8 Feb - 2 Mar): Basic range 0-100 m; Transmitter 1/1, Bandwidth and pulse length 3 KHz, 0.6 ms; TVG and GAIN 20 log R - 0 dB; Recorder gain 2; Transducer ceramic 10 degr. circular. QM integrator: Gain 10 dB x 10, threshold 0.8 SL+VR = 116.1 dB (Calibration 11 Feb 1982 on standard sphere). SONAR: Fixed at 90 degr. starboard. Schools within range.
EK 400/120 KHz (2 Mar - 4 Apr): Basic range 0-100 m; Transmitter High, Bandwidth and pulse length 3.3 KHz, 1.0 ms; TVG and GAIN 20 log R - 0 dB; Recorder gain 3; Transducer ceramic 10 degr. circular.
Sonar ST 24 KHz, Basic range 0-500 m; Transmitter normal; Bandwidth broad; Pulse length 3 ms; Gain 2-3; AGC normal; Tilt 4-6 degr.; Direction fixed at 90 degr. starboard. Schools within range 100-280 m counted as sample of school density.
Sonar Skipper S 109/180 KHz: Is newly installed and only some pilot studies are carried out. The sonar is successfully coupled to the recorder of EK 120, but the system is not yet fully optimized.
Towed transducer: Some experiments with the towed transducer were made in order to assess resources close to the surface in shallow waters. The 120 transducer were tilted 10 degr. towards the surface and the body was towed at full speed in 11 m depth.
Heavy noise from the propeller occurred and the experiment was interrupted by bad weather. Further development of the system seems possible.
Hydrography
Temperature, salinity and oxygen content was sampled at standard depths with Nansen bottles. Oxygen was measured with Winkler method and salinity determined with 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, height during trawling abt 6 m. Pelagic trawls: Type "Harstadtrawl", meshsize codend 21 mm. Width abt 30 m, vertical opening abt 15 m; Type "krilltrawl", abt same size as "Harstadtrawl" but with codend meshsize 9 mm.
Figure 1. Survey routes and stations 8 Feb - 1 Mar 1982.
Figure 2.
Survey routes and stations 3-8 Mar
Survey routes and stations 8-17 Mar
Figure 3. Survey routes 17-20 Mar.
Figure 4. Survey routes and stations 20 Mar - 3 Apr.
Figure 5. Surveillance of fishing vessels in Mauritania.
Figure 6 Surveillance of fishing vessels between Cape Blanc and Cape Juby.
Figure 7. Surveillance of fishing vessels between Cape Juby and Agadir.
Figure 8. Temperature in surface layer 15 Feb- 1 Mar 1982, Freetown-Cape Verde.
Figure 9. Temperature in surface layer 3- 17 March 1982, Cape Verde-Cape Blanc.
Figure 10. Temperature in surface layer 17-20 Mar 1982 Cape Blanc-Cape Juby.
Figure 11. Temperature in surface layer 23-30 March, Cape Juby-Agadir.
Figure 12. Fish distribution 11 Feb- 1 Mar 1982, Freetown-Cape Verde.
Figure 13. Fish distribution 8- 17 Mar 1982, Mauritania.
Figure 14. Fish distribution 17-20 Mar 1982, Cape Blanc-Cape Juby.
Figure 15.
Fish distribution Cape Juby- Agadir, 23-30 Mar
Fish distribution Cape Juby-
Agadir, 1-3 Apr
