FISHERY RESEARCH 337 



year. Observations must be carried through without fail 

 from year to year, almost it seems indefinitely ; for until 

 many years are so covered no possible light can be thrown 

 on the causes of the great natural fluctuations of the fish 

 supply, of good or bad " survival years." 



Research has also shown that it is not sufficient merely 

 to study the conditions of the area with which one is 

 concerned. It is necessary to know the sequence of events 

 in other far lying regions, for all the waters of the oceans 

 bear an intimate relation one with another in their current 

 systems, and an alteration in the trend of a current in one 

 locality may have far reaching effects on the conditions 

 for life in waters many miles away. The fisheries of the 

 North Sea are influenced to a large extent by that north- 

 easterly drift of the Gulf Stream which, rounding the 

 north coast of Scotland, turns southwards into the North 

 Sea itself. That the Gulf Stream is subject to pulses seems 

 now most probable, running one year with full force and 

 penetrating far into the North Sea, and another year 

 weakly. It seems that some of these pulsations may be 

 rather tidal in nature, for it has been shown for two years 

 at any rate that an increased flow of the Gulf Stream took 

 place when the moon was at its nearest point to the earth 

 and therefore exerting a greatest attraction on the earth. 

 The periods of the moon's proximity to the earth, or 

 nodapside, occur in eleven and a half yearly cycles. Suppose, 

 therefore, that an increased flow of the Gulf Stream were to 

 have a pronounced effect on the extent and distribution 

 of the herring fisheries in the North Sea,- and of this there are 

 indications, then here is a definite means of preparing the 

 industry for a good or bad year long in advance. 



So far this chapter has outlined the type of research 

 into fishery problems that is carried out at sea in specially 

 equipped research vessels. There remains another side 

 to fishery research of no less importance. The results of 



