154 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



inshore in Liverpool Bay the plaice population of the first two 

 years of age is a relatively fixed one. Therefore the young 

 fish of about 4-12 cms, such as are caught in the shrimp trawl, 

 become the older fish of about 10-30 cms, which are caught in 

 the fish trawl one or two years later. 



Obviously the figures discussed here indicate that there 

 is a periodicity in the abundance of plaice in the shallow 

 water grounds of Liverpool Bay, and it is very likely that the 

 same periodicity would have been observed in other inshore 

 areas off the west coast, say in Morecambe Bay and the Solway. 

 Since these shallow water areas are " nurseries," we should also 

 expect that the same periodicity might have been traced in 

 the catches of plaice made by the smacks and steam trawlers 

 working on the deeper grounds offshore. 



The observations made here have some relevancy in regard 

 to the much- discussed question as to whether or not the 

 restrictions on fishing for the period 1914-19 have led to an 

 increase in the density of plaice on the fishing grounds. If the 

 periodicity noted in Liverpool Bay holds for other grounds, it 

 would not be sufficient to compare the pre-war and post-war 

 years without taking it into account. 



