204 POPULATION'S OF THE SEA 



and communities, but its greatest value lies in the quantitative 

 expression of migrations and other fluctuations in abundance and 

 distribution, and the study of their possible causes and effects. 



The systematic collection of physical and chemical data is be- 

 coming routine and, recently, there has been an improvement in 

 the recording of commercial fishery statistics. The techniques of 

 fisheries biology were discussed at a symposium of the member 

 countries of the International Commission for the Northwest At- 

 lantic Fisheries at Biarritz in 1956. Reporting on this meeting, 

 Lucas (1958) wrote, "Attention was drawn to our relatively scanty 

 knowledge of the ecology of the plankton and particularly of the 

 distribution of the eggs and larvae of commercial fish . . ." . 



I shall concentrate on the plankton, therefore, although similar 

 remarks could be made about all forms of marine life. Most of 

 my material is taken from the Continuous Plankton Recorder 

 Survey. I have done this partly because the survey is carried out 

 from my own laboratory in Edinburgh and partly because it pro- 

 vides an example of a standardized method of sampling used 

 over a long period of years. 



Some Examples of Shapes of Distribution 



Nearly all the illustrations which follow are taken from the 

 work of Mr. J. M. Colebrook and Mr. G. A. Robinson who are 

 making a special study of the dynamics of the distribution ot 

 plankton based on the Recorder Survey. I am indebted to these 

 two colleagues and also to Dr. M. H. Williamson for many sug- 

 gestions and discussions. 



The Continuous Plankton Recorder was designed for use from 

 commercial freighters on their normal sailing schedules (Hardy, 

 1939). It is towed at a depth of 10 m, sampling the plankton con- 

 tinuously on a moving band of bolting silk. From 1932 to 1939 it 

 was used mostly in the North Sea, but after World War II, the 

 sampling was gradually extended to include a comprehensi\'e 

 cover of the northeastern Atlantic. This was made possible by the 

 introduction of the Ocean Weather Ships which began to tow 

 Recorders in 1948. 



