iv 
to 1862. The gradual increase in quantities cured due to improved 
fishing vessels * had to be considered also. 
Plotting out the monthly values for range of tide showed 
considerable differences throughout the period, and to obtain 
data in a form considered suitable for the purpose, the differences 
between the spring and autumn maxima and the summer and winter 
minima have been found and summed for each year. These are 
given in Table IT. 
It has been, stated before when reporting on herring investiga- 
tions that it was not considered the hydrographic conditions 
obtaining during the year of capture were the chief factor which 
determined the productivity of the fishery, and the opinion has 
been expressed that the conditions at the time of hatching were 
of greatest importance. This and the fact that the east coast 
fishery of Scotland depends chiefly upon the abundance of fish 
with three winter rings on their scales determined a comparison 
between tidal data and the catches made three years later. The 
result was not satisfactory. 
The samples from spring spawning shoals in 1921, following 
the abnormal activity of Atlantic waters in 1920, showed for the 
Firth of Forth and Broad Bayt what was considered to be an 
abnormal number of spawning herrings at the end of the third 
growth period. The sample from the north coast of Sutherland- 
shire in the same year contained also what was considered a high 
number of herrings of this age. Further sampling in the spring 
of 1922 has made it quite clear that the high numbers of these 
young fish were not due to accidental sampling. 'The cccurrences 
of these young fish in what is considered to be abnormal numbers, 
and the fact that in 1903, a year in which Matthews { considered 
conditions abnormal over the larger part of the northern European 
area, Fulton § found cod spawning in autumn in the North Sea 
suggested a new working hypothesis when considering fluctuations 
in catches and hydrographic data. This hypothesis is that the 
conditions preceding the year of spawning are of greatest 
* See “ Post-war Problems,’ Lieut.-Commander D. T. Jones, R.N.R. Fish. Bd. for 
Seot., Annual Report, 1918, page 3. 
+ Report, New Series X., page 90. 
+ Report on the Physical Conditions of the Fnglish Channel and adjacent waters, 1904 
and 1995, page 293. North Sea Invest. Committee, 2nd Report, Souther area, Cd. 4641, 
§ Pub. de Cire., No. 8. 
