FLUCTUATIONS IN THE SUPPLY OF HERRING 
33 
late years of area 6 during the month of June. 
The reasons for these differences in general trends 
of abundance will be discussed more fully below. 
mean) of the percentages that the average 
weekly catch per boat is of a standard curve 
(see text) 
'igwre 20.— The standard curve for average weekly catch per boat for 
Group III (see text) 
LEVELS OF ABUNDANCE IN DIFFERENT AREAS 
2. S' 
An attempt was made to discover whether the 
general trends of abundance indicated in the fore- 
going analyses were caused by general changes in the level of abundance in all areas 
fished or whether each area had its own 
level of abundance. In determining the 
abundance in an individual area it is not 
feasible to use either the catch per boat per 
week or the number of deliveries, as both 
depend chiefly on the relative abundance in 
otherareasinwhichfishare being taken. Re- 
sort was made, therefore, to the average size 
of catch as it is to a larger extent free from 
the shortcomings of the other methods. 
The simple computations involved are 
presented in Table 7 and Figure 21. Fig- 
ure 21 reveals the striking fact that the 
general level of abundance in each area 
under consideration is in inverse order to 
the length of time during which it has been 
subject to exploitation on any scale. Areas 
11 and 12 have been exploited since the 
founding of Killisnoo in 1882, and areas 14 
2.2 
\o 
V 
\ v 
x \ \ 
\-..y x 
„ ? , 9. X \ 
\\ \ 
\ A 
\ 
\ 
X 
/ 
\ 
jr&/2 
7 
/&2G /&27 /928 /S2S 
Figure 21.— Showing the logarithms of the actual catch (un- 
weighted) in several statistical areas for different years (see 
fig. 9) 
