SEA-FISHERIES LABORATORY. 285 



in this area fishermen have captured, in one year, about 

 45 per cent, of all the plaice present on the ground which 

 were over eight inches in total length. 



I think that too much may easily be made of this 

 argument. It would be justifiable to make the percentage 

 of marked plaice returned indicate the intensity of plaice 

 fishing if the marked fish behave normally; if, when 

 liberated, they spread themselves uniformly over wide 

 areas. Then it may reasonably be contended that the 

 proportion of marked fishes re-caught represents also the 

 proportion of the unmarked fishes caught. I think 

 that the marked fish behave normally, but it is the case 

 that there is a certain amount of segregation in the distri- 

 bution of the marked fishes. The figures indicating 

 " intensity of fishing " are to be regarded only as 

 approximate indications of the degree of exploitation of 

 the local fishing grounds. 



On the other hand, the results of the Luce Bay and 

 the Welsh experiments indicate a much less intensity of 

 fishing. In Luce Bay and the adjacent waters this is 

 accounted for by the anti-trawling legislation of the 

 Scottish Fishery Board. Plaice are only caught in this 

 area by lines, trammels, and other forms of fishing, which 

 are very ineffective when compared with trawling. But 

 in the Carnarvon Bay experiment this is not the case. 

 The low proportion of fish returned, 12 per cent., is due 

 only to the fact that there is very little fishing indeed in 

 Carnarvon and Cardigan Bays when compared with the 

 Coasts of Lancashire, Cheshire, and that part of the North 

 Welsh Coast exploited by Hoylake smacks. The same is 

 to be said of the other Welsh experiments, for though the 

 complete year has not yet elapsed it is apparent that 

 nothing like the same proportion of fish as in the case of 

 the Lancashire experiments will be returned, 



