TILSETH and ELLERTSEN: FOOD ORGANISMS OF LARVAL COD 



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22-24 Apr. 81 Austnesf jorden 

 01 05 09 13 17 21 01 



FIGURE 4. — Isopleth diagrams of the particle concen- 

 trations (per liter) (A), and nauplii (per liter) (B), center 

 station, section 5 in Austnesfjord, 22-24 April 1981. 



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22 -24 Apr. 81 Austnesf jorden 



01 05 09 13 17 21 01 05 09 H 



Austnesfjord is presented in Figure 4A and B. The 

 maximum observed particle concentration was a 

 small patch of 50 particles/1 at about 15 m (Fig. 4A). 

 A patch of 40 nauplii/1 at the same depth was iden- 

 tified from pump samples (Fig. 4B). The particle/ 

 nauplii isolines in the upper 20 m show a tendency of 

 ascending towards the surface at midnight, indicat- 

 ing their diel vertical migration. This observation was 

 repeated on another 24-h station made 6 d later at the 

 same position (Fig. 5A, B). Particle concentration 

 had increased markedly during this period; more 

 than 50 particles/1 were found at 25-35 m depth on 

 every profile. A very dense surface patch was found 

 at midnight with more than 500 particles/1. Figure 5B 

 shows a similar distribution of nauplii during the 

 same 24-h station. Since there was no wind in the 

 fjord and consequently little or no vertical turbulence, 

 the hydrographic conditions during this 24-h station 

 were perfect for this type of observation. This is 

 shown in Figure 6 where the hydrographic conditions 

 is presented by the temperature distribution in the 

 upper 60 m. 



Figure 7AandB presents the particle (1 50-600 jiim) 

 distribution from to 40 m depth through a section of 

 the Austnesfjord made at night on 27-28 April 1981 

 from 2130 to 0420 h. There was little or no wind in the 

 fjord when the section was made. Patches of more 

 than 100 particles/1 were found in the surface water 

 of the outer parts of the fjord. A particle minimum 

 layer (<10/1) was observed at 10 m in the middle of 

 the fjord. In the bottom of the fjord three patches of 

 more than 50 particles/1 were found at different 

 depths. Figure 7B shows the naupliar distribution on 

 the same section. Highest concentrations (> 100/1) 

 were observed in the bottom of the fjord, at inter- 

 mediate depths and in the surface water of the outer 

 parts of the fjord. 



The same section made through the fjord the next 

 day from 0950 to 1610 h (Fig. 8A, B) showed that the 

 particle/nauplii distribution in the fjord had changed 

 completely. A particle/nauplii minimum layer (< 10/ 

 1) was found from the surface down to about 20 m 

 through most of the fjord length. The surface patches 

 in the outer parts of the fjord had disappeared. Only 



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