RECENT HYDROBIOLOGICAL INVESTIGATIONS 615 



dition of the cod-fishery and the temperature of the sea. The 

 higher the latter, the later in the year do the cod-shoals approach 

 the fishing-grounds : that is to say, a strong Gulf Stream flow 

 corresponds to a late fishery, and generally a rather poor 

 fishery ; and, conversely, a weak Gulf Stream flow corresponds 

 to an early, and generally a good fishery. Further — and this is 

 a point of the greatest practical importance — it is possible to 

 predict the approximate date at which the fish may be expected 

 to reach the fishing-grounds, the date of the maximum fishery, 

 as well as the probable yield of the season's operations ; for a 



I 1901 

 H IE 1902 



1902. 

 igoh 



1905 



190s 



190s 



190b JQ 



3°T 



2.°.. 



1°- 



o°l 



FiG. 7. — Sea-temperature at Sognefjord in May, air-temperature at Lofoten, and 

 phase of cod-fishery at Lofoten in the following year. 



(From Helland-Hansen and Nansen, loc. cit. p. 351.) 



high average sea-temperature at Sognefjord in May corresponds 

 to a high sea-temperature at Lofoten about a year later. These 

 conclusions are based, it is true, on only four or five years' 

 observations, the period during which the International Hydro- 

 graphic Investigations have been in progress, but other cor- 

 roborative evidence is available. The total catch of the season 

 and the air-temperatures are recorded since 1880, and it is seen 

 that a fairly close parallelism holds for this period of years : the 

 higher the air-temperature at Lofoten — that is, the stronger the 

 Gulf Stream flow — the lower is the proportion of cod caught 

 before March 15 of the same year, 



