SEA-FISHERIES LABORATORY. 237 



preferred to remain in Liverpool Bay they wonld probably 

 not be any more numerous than they are at present. There 

 are fewer fish of six years old than there are of five, fewer of 

 five than there are of four, and so on, and therefore trawling 

 affects the abundance of larger fish more than it affects that of 

 the smaller ones. There is so much trawling in Liverpool Bay 

 that the abundance of these larger fish would be kept down, 

 even if the grounds were natural ones for such plaice. 



On the other hand we do seem to have an accumulated 

 stock of plaice in Luce Bay. We have reasons for believing 

 that fish that have spawned on the northern grounds migrate 

 into the Bay when they become spent. They are protected 

 there because trawling is effectively prohibited by the Fishery 

 Board for Scotland, and the other methods of fishing that are 

 practised are probably quite insufficient to bring down the 

 numbers of the big plaice (up to 65 cms.) that are found there. 



Did a Stock of Large Plaice accumulate in the Irish Sea during 

 the War Years ? 



We have discussed this question in the preceding pages 

 and find that there is no very good evidence that such an 

 accumulation took place. 



Our conclusion is, therefore, that there is no reliable 

 evidenca in favour of the conclusion that there is an impoverish- 

 ment of the plaice grounds of the Irish Sea due to over-fishing. 

 But it may be said that the plaice there " run rather small " 

 and that they might get bigger and so become commercially 

 more valuable if there were size-limits, or restrictions of other 

 kinds. This further question must briefly be considered. If 

 we could, by any means, raise the prevalent size of plaice from 

 (say) 23 to 30 cms. the same total weight of fish landed would 

 be more valuable. If, further, we could so legislate that (he 

 same numbers of plaice would continue to be caught, but that 



