246 



DISCOVERY REPORTS 



These bottom temperatures are particularly important in their relation to the most promising fish 

 of the region, the Patagonian hake. It is quite clear, from the general run of the figures, that these are 

 plentiful at some seasons in waters where the bottom temperatures are around 6° C. Their lower 

 hmit seems to be some 3° below the figure 87° C. which Hickling (1927, p. 67; 1928, pp. 81-2, 88) 

 found to be the normal cold limit of penetration of European hake. The ' stumpies ' of the Norwegian 

 deep are commonly found at lower temperatures, it is true; but Hickling 's later work provides ample 

 evidence that they are a local race, unrepresentative of the main stock, quite apart from the tem- 

 perature of the waters in which they are found (Hickling, 1930ft, pp. 50-1). 



The bottom temperatures north and south of that part of the shelf represented by our 'partly 

 hypothetical cycle' seem to vary with the seasons in similar fashion. To the north they probably 

 'average' 1° C. warmer, and to the south perhaps 1° C. colder (certainly so in summer). The main 



JULY I AUG I SEPT OCT NOV I DEC I JAN I FEB I MAR I APR I MAY I JUNE 



Fig. 6. Bottom temperature on the shelf; partly hypothetical annual cycle for the intermediate region, 

 corrected to an assumed mean depth of 100 m., with surface cycle for comparison. 



feature is the lag of at least a month after the surface maximum, and the relatively high autumn and 

 winter values due to mixing. For this reason the seasonal graph does not fall anything like so steeply 

 as does that showing the surface temperatures, from the maximum to midwinter. 



Observations of the nutrient sah content of the waters of the Falkland current are not yet available 

 for this area. 



PLANKTON 



During the trawling surveys some phytoplankton samples were collected from the waters of the shelf 

 with the Gran net. They have not been fully analysed because of pressure of other work. Most were 

 obtained during the third survey. Mr Rayner made some preliminary observations on them (un- 

 published) and has recorded his impression that they indicate a poorer phytoplankton than that found 

 off the west coast of South America. Some of our early phytoplankton work in the ' Discovery H ' 

 extended northwards, to the extreme south of the trawling survey area, and there we found some 



