74 
fact that few hydrographic data are available for years previous 
to 1904. 
A comparison of catches with salinity data was begun, and the 
data available for the English Channel, which have been reported 
on by Dr. E. C. Jee,* were used. The period covered is considered 
much too short. Except for a possible connexion between a high 
salinity early in the year, followed by a gradual decrease during 
the year of hatching, and a subsequent good year-class, nothing 
was found worthy of note. 
Owing to the war it was not until some time towards the end 
of 1920 that Professor D’Arey Thompson’s paper on “ Mean Sea 
Level and its Fluctuations” + came to my notice. The range of 
tide, or interval between mean high and mean low water, for 
Aberdeen suggested a possible connexion between hydrographic 
conditions, as indicated by tidal phenomena, and herring catches. 
The mean monthly values, in feet, for this range for the period 
1862 to 1913 were as follows :— 
ETE. TM. + 0V.. Vee ay Vale VAUUL? XS © PS ee 
9-01 9-14 9:25 9-27 9-12 9-04 9-12 9:34 940 9:25 9-01 8-86 
Maxima occur in March-April and August-September, and 
they coincide, practically, with the two chief spawning times, 
spring and autumn. 
The only data available which gave an indication of the pro- 
ductivity of the fisheries over so long a period were the quantities 
of herrings cured in Scotland. 
The nineteen-year period found by Professor Thompson for 
mean annual inter-tidal range at Aberdeen gave a curve which 
suggested a further relation between tidal phenomena and good 
years in the East Coast fishery, and a smoothing of the yearly 
herring cure of the East Coast in groups of three and five years 
hinted at the possibility of there being two maxima for herring 
catches in a nineteen-year period, one coming after the maximum 
for tidal range and the other following the minimum. In this 
connexion the herrings cured were dealt with from 1816, and the 
nineteen year period was assumed to hold good for the years previous 

* Bd. of Agric. and Fish. Fish. Invest., Series ITI. Hydrography. 
} Fisheries, Scotland. Sci. Tnvest., 1914, IV. 
} Fishery Bd. for Scot. Annual Report, 1920, pp. 128-131. 
