142 WHITING 



fiand hoppers (amphipods), which formed their principal 

 nourishment. Hjort points out that these small crustaceans 

 are extremely numerous in some places on the sea-bottom, and 

 entirely absent in others of the same depth and temperature. 

 Their presence or absence must therefore depend on the currents 

 at the bottom ^ ; and on their presence or absence will depend 

 whether fishermen do or do not find shoals of young fish on 

 these grounds. Here is a good instance of the direct connexion 

 between research into the microscopic life of the sea and 

 commercial fishing, which, to the best of the writer's behef, 

 has never been explained to fishermen. 



1 Hence one good reason for measuring bottom currents with ' bottom 

 trailers '. 



