SEA-FISHERIES LABORATORY. 229 



increased, and, on the whole, better catches seem to have 

 been made. But the evidence brought forward in this report 

 also shows, we hold, that this variability in the size and 

 abundance of the plaice inhabiting the Irish Sea is something 

 that happens, " of itself," that is, quite apart from the influence 

 of the fishing fleets. Throughout the period 1892-1920 there 

 is good evidence of a natural fluctuation in the abundance of 

 plaice, some series of years being very good, while others 

 are relatively very bad. The evidence we refer to is all 

 experimental, but it is backed up by what we do know about 

 the fluctuations in the quantities of plaice landed by the 

 steam vessels and other trawlers working in the Irish Sea 

 area. Further, the conditions in the English Channel seem 

 to resemble those obtaining in the Irish Sea. 



If there had been no war, and no restrictions on fishing 

 in the Irish Sea, the result to have been expected would have 

 been just that which we actually observe — the progress of a 

 natural fluctuation in the abundance of plaice. If only the 

 measurements and other data which we give here, or which 

 are otherwise obtainable, were at our disposal, and no knowledge 

 that there had been a state of war during the years 1914-1918, 

 we should have been quite unable to deduce the latter. All 

 we should have known would have been that, for some reason 

 or other, vessels did not go to sea so frequently in 1914-8 as 

 they did in the year previous to 1914. 



These results obtained from a study of the West Coast 

 fisheries naturally make us cautious in accepting, without 

 reservation, the conclusion that the effect of the war restrictions 

 was an increase in the stock of plaice inhabiting the North 

 Sea. The natural fluctuation which, we believe, characterised 

 the Irish Sea during the years 1892-1920 may, quite reasonably, 

 be supposed to have characterised the North Sea also : it is to 

 be noted that the statistical information relative to the latter 

 area is very defective for the years before 1908, and between 



