RECENT HYDROBIOLOGICAL INVESTIGATIONS 621 



from this current mixes with water flowing from the north, 

 or from the coastal regions, that the richest plankton is to 

 be found. In those years in which the intensity of the Gulf 

 Stream is least, there is probably a more extensive mixture than 

 usual of truly Atlantic and Polar water. If the hypothesis 

 suggested by Helland-Hansen and Nansen is borne out, it is 

 therefore the abundant food-stuff contained in this Polar water 

 which is the factor favourable to the nutrition of fishes. It is 

 conceivable that the low temperature is itself a factor leading to 

 increased nutrition, but the latter effect is most probably to be 

 traced to several causes. But, however this may be, the relation 

 of a strong Gulf Stream flow, as evidenced by a high tempera- 

 ture and salinity, to a relatively poor fishery, is one which 

 is likely to be of very great practical importance. 



It is impossible to avoid speculating on the causes of this 

 larger periodicity of the Gulf Stream flow. The latter waxes 

 and wanes throughout the year, attaining a minimum in our 

 latitudes during the autumn, and rising again to a maximum in 

 the spring. But a larger periodicity is superposed upon this 

 yearly one, a period of how many years we do not yet know, 

 for the International Hydrographical Investigations have not 

 been carried on sufficiently long. But if we admit that the 

 larger fluctuations in air-temperature in these countries, which 

 are influenced predominantly by the Gulf Stream drift, are to be 

 traced to the variations in the strength of the latter, then a 

 cause suggests itself. In fig. 8 the curve of relative numbers of 

 sunspots is represented, and it will be seen that the fluctuations 

 in the numbers of sunspots observed during the period 1874-96 

 are roughly similar to the fluctuations in the productivity of 

 the Lofoten cod-fisheries. 



Sooner or later a connection between the sunspots and the 

 abundance of fishes in a part of the sea was certain to be 

 suggested, and one is prepared to be sceptical as to the value 

 of such a comparison. But it appears to me that the data 

 quoted by Helland-Hansen and Nansen afford good grounds 

 for regarding the hypothesis as a working one. A fairly large 

 volume of evidence has been collated by Arrhenius to show 

 that many phenological, climatic, and other phenomena are to 

 be associated with these paroxysms in solar activity. On the 

 one hand, it appears impossible to seek for any other cause 

 of the greater variations in the intensity of the Gulf Stream 



