59 



The relationship of measurement to weight has been estab- 

 lished since the formula was introduced for other species, even to 

 round fish. It is csp< cially interesting with reference to the latter 

 to find that the general " straight line " relationship of the various 

 measurements is a fact of growth. 



This estimate of the population of the inshore fishes has 

 another importance. It was found in the case of plaice that the 

 number of marked fish returned from the captures made by fisher- 

 men amounted to 14 per cent. This is doubtless a small number, 

 and the Scottish and other marking experiments with reference 

 to larger plaice show that 40 or even 50 per cent, of the marked 

 fish may be returned. Suppose we assume that in the inshore 

 waters the line fishermen capture 20 per cent, of the population 

 about 9 J inches, then the Northumbeiland population of plaice 

 of the larger immature sizes is about 546,500. The plaice con- 

 cerned are for the most part of three to six winters. They are 

 the survivors of the two preceding groups, Groups 1 and 2. Now, 

 if we take the analysis of the experiment made this } r ear at Skate 

 Roads on September 2nd, which showed that 130 were captured 

 of 1 and 2 groups and 52 of the older groups, as indicating the 

 degree of survival, this amounts to 40 per cent.. Let us say 30 

 per cent., for the smaller of the younger stages are less like!} 7 to 

 be captured, and it can be said that the young plaice of the inshore 

 waters of Northumberland amount to some 1,821,700. The 

 inshore waters then must be looked upon as performing an 

 important function in receiving and supporting, and to some extent 

 protecting, a large population of the food fishes. 



An inspection of our previous experiments shows that the 

 survival above 20 cm. is variable, but is usually above 30 to 35 

 per cent., so that the above computation is likely not far from the 

 truth. In a good year it may be said that the inshore plaice of 

 Northumberland amount to over two million. 



If this be an indication of the wealth of the North Sea, in a 

 small narrow tract like the territorial waters of Northumberland, 

 how much more must the plaice population of the important 

 nurseries in the southern North Sea be regarded. From tha 

 immense spawning grounds of the southern part of the North Sea 

 large crowds of larvae are carried to the continental coast and give 

 rise to an inshore population which must be reckoned in millions. 



