THE IMPOVERISHMENT OF THE SEA. 15 



impossible to judge of the effect of the closure of the Scottish bays 

 from figures calculated upon this basis. 



Yet, if a table be drawn up setting forth the yearly frequency of the 

 monthly surveys actually carried out in the two areas, it will be seen at 

 once that, with the single exception of June, the proportion which the 

 number of surveys in either area bears to that in the other area for the 

 first quinquennial period is never exactly repeated for the second quin- 

 quennial period — a lack of co-ordination which necessarily biases the 

 combined averages and precludes any exact comparison between the 

 two periods by the methods which Dr. Fulton has pursued. Thus for 

 January the average from one year's survey in St. Andrews Bay and 

 one in the Forth in the first period is contrasted with the average 

 derived from one survey in the Bay and five surveys in the Forth 

 during the second period. For February the average for the first period 

 is based exclusively on surveys in the Forth, and this is contrasted with 

 an average for the second period derived from four surveys in the Bay 

 and five in the Forth. For March the average is derived from two 

 surveys from each area in the first period, but from a combination of 

 three St. Andrews surveys with four Forth surveys in the second, and 

 so on, the general tendency being to give the Forth a preponderating 

 influence on the combined averages, which is considerably greater 

 during the second period than the first. The only exceptions are June, 

 in which the proportion of surveys in the two areas is the same in the 

 two periods, and February, July, and November, for which months the 

 Bay exercises a greater influence on the averages for the second period 

 than for the first. 



Leaving these exceptional cases out of consideration for a moment, 

 we may trace the general tendency of this excessive influence of the 

 Forth on the averages for the second period by reference again to the 

 data contained in Table I. 



In the case of plaice, owing to the productivity of the Forth in this 

 species being much lower than that of St. Andrews Bay for all except 

 the three winter months, there can be no doubt that a preponderating 

 influence of the Forth on the combined averages for the second quin- 

 quennial period must tend, ceteris paribus, to depress the average for 

 plaice below its value for the first period, thus fallaciously producing 

 an appearance of a diminution in the numbers of plaice in the com- 

 bined areas, even when no such diminution may be apparent from the 

 figures for the two areas taken separately. 



If lemon soles are added to plaice, as in Dr. Fulton's last figures, 

 such inclusion will not materially affect the figures for St. Andrews 

 Bay, but will increase those for the Forth to an appreciable extent in 

 the summer months ; but even under these circumstances the Bay 



