130 SEA FISHERIES 



no means of absolute value ; they change according to 

 locality ; nevertheless they denote a fairly universal period 

 of spawning and development. In short, the temporary 

 reservation is on the whole sufficient; but it would be 

 useless if, instead of re-establishing it annually in the same 

 place, we were to shift it along the coast. Let us have 

 plenty of reserves permanent when the thing is possible, 

 and in all other cases temporary. 



II 



The question of which I have just treated from an 

 empirical point of view is connected with that of the 

 movement of those fishes which live on the bottom ; 

 a question of which the solution has been sought by 

 scientific methods. I refer to the experiments under- 

 taken in the North Sea by means of marked fishes. A 

 batch of fish is captured at a given spot; the experi- 

 menters satisfy themselves that the individual speci- 

 mens have suffered no lesion and are well and lively ; 

 they attach to the back of each a little oblong label 

 having a number, or perforate one particular fin with 

 a punch of determined shape ; finally all the fish are 

 returned to the sea at the same spot. The fishermen of 

 the neighbouring ports are invited, in return for a small 

 reward, to advise the Committee of Inquiry whenever 

 they capture any of these fish in their nets. It is thus a 

 simple matter to estimate the distance travelled by the 

 latter in a given number of days. The best known of 

 these experiments was carried out in St. Andrew's Bay, in 

 Scotland. Of 1,250 plaice, 103 were retaken, which in 

 239 days had travelled a distance of 6 miles. Of 337 

 dabs released, n were retaken ; the average time was 178 

 days, the average distance 37 miles. Of 196 cod, 10 were 

 retaken ; average time, 74 days ; average distance, 52 



