138 TRANSACTIONS LIVERPOOL BIOIOGICAL SOCTETY. 
of fish actually landed show that there was a tendency to a 
maximum of abundance in these years. 
So we must reconsider Captain Eccles’ statistics enquiring, 
first of all, whether or not there have been 
Changes during the period of war? 
No doubt at all there must have been a decrease in the 
amount of fishing going on in the offshore waters during the 
years 1915-7: has this affected the productivity of the shore 
grounds ¢ It is very difficult to say whether or not this has 
been the case. At first, we might think that if there have been 
fewer fish (say plaice) caught offshore there ought to have 
been more and larger fish caught inshore. Now, the diagrams 
on pp. 134 and 135 seem to show that there has been an actual 
decrease in the numbers of plaice caught on the Mersey (inshore) 
grounds during the period 1910-1917. The minimum of 
abundance may have been in 1915, 1916, or 1917: itis difficult 
to say until we have several years more statistics. But there 
has been no certain increase—that we may be pretty sure 
about, nor has there been an increase in the size of the plaice 
caught durimg the years of war. 
Prevalent sizes of plaice caught on the Mersey grounds. 
We can best study the variations in length of the plaice 
landed by taking “ shortest half-ranges.” We make a curve 
of the sizes of the fish caught for any month, or year, or group 
of years, and then find what are the sizes of the plaice caught 
most frequently. Thus let the followimg diagram represent 
a catch :— ! 
16-17 
17-18 
18-19 
19-20 
20-21 
etc. 
Centimetres of length. 
