PRIMARY PRODUCTION 



S33 



and length dimensions of herring concentrations and movements 

 will be of the same order as the plankton ones, and this statistical 

 distribution is all that one may i)e able to predict about their 

 detailed behavior. 



In studies of this kind, some of the varial)ility can be removed 

 by going to the opposite extreme from a homogeneous hydro- 

 graphic situation and choosing an area where there are very large 

 hydrographic changes in short distances. This is found at the edge 

 of the Baltic outflow up the Norwegian side of the North Sea, 

 where a layer of cold fresher water overlies the typically warm.er 

 and more saline North Sea water. In early spring this layer is very 

 productive when the rest of the North Sea is not due to the latter's 

 vertical homogeneity. The resulting distributions for a small part 

 of this edge are shown in Fig. 7 where the stations are 10 miles 

 apart. In the temperature chart the position of the edge was found 

 with a surface thermograph. The phosphate and chlorophyll data 

 show how marked the production changes are at this edge. On the 

 fourth chart the edge has been drawn in and shows that the her- 



55 - 6 5 \[ 



Temp CO 



Phos Cpq at/L) 



Chlor (mg/in^) 



erring traces 



Fig. 7. Distributions at a sharp hydrographic "edge. 



