CHAPTER IX. 



THE PEODUCTIVITY OF THE SEA. 



It should hardly be necessary to warn the reader that he must 

 not interpret the phrase " Census of the Sea " in too literal a 

 manner. The enumeration of the population of a country with 

 respect to the age, sex, occupation, &c., of the individuals com- 

 posing it is a process which is carried out with a high degree of 

 accuracy, and I do not for a moment suggest that any enumeration 

 of the individual organisms inhabiting a part of the sea can be 

 made with such pretensions to accuracy. The materials from which 

 such enumerations are made are (1) quantitative plankton investi- 

 gations; (2) fishing experiments: and (3) the commercial fishery 

 statistics. Now the plankton investigations claim to give only 

 rough approximations to the truth: fishery experiments cannot be 

 made so as to give absolute values for the numbers of fishes and 

 other animals residing on the sea bottom; they can only afford 

 relative values for the density of life in the sea; and the commercial 

 fishery statistics are so imperfectly collected that their use for any 

 scientific purpose generally leads to disappointment. What then 

 is one to do if he wishes to form any idea as to the quantitative 

 distribution of organisms in the sea, or in fresh water ? With 

 such imperfect methods and data only rough approximations can 

 be made. It is no service to science only to urge " counsels of 

 perfection," one should rather make use of what data are available, 

 and trust that the provisional results thus attained may assist in 

 the further elaboration of methods of investigation ; and even if we 

 are unable to give accurate figures for the population and pro- 

 ductivity of the sea, it is always of interest to know what are the 



