70 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



banks, and these are just the places where of recent years it has 

 been found that plankton is also most abundant. 



Any naturalist cruising on the West of Scotland (and no 

 doubt in any other region where there are strong tides) could 

 scarcely fail to notice the way in which the gulls and other 

 sea-birds congregate where the currents run most strongly and 

 where there are swirls in the water, indicating rocks or an 

 uneven bottom, and resulting vertical movements of the water. 

 These sea-birds are found to be feeding upon young fish, and 

 the fish are there because the plankton is unusually abundant. 



A definite connection seems to have been established on 

 the coast of Cornwall, by Allen and Bullen, between the results 

 of the mackerel fishery and the occurrence of Calanus in the 

 plankton. There is some evidence that on the West coast of 

 Scotland there is a similar connection between herring shoals 

 and abundance of Calanus* The matter is well worthy of 

 further investigation. 



Many groups of the plankton, and especially the zoo- 

 plankton, it is now known quite definitely, are distributed in 

 swarms — notwithstanding various assertions to the contrary. 

 In our coastal seas at least, where the fisheries we are interested 

 in take place, the plankton is not uniformly distributed. 

 Various localities and depths are characterised at different 

 seasons by particular assemblages of plankton, and it is reason- 

 able to believe, in view of the facts given above as to the 

 association of fish and plankton, that these variations in the 

 distribution must have a marked effect upon the presence and 

 abundance of at least such fish as herring and mackerel, and 

 also of the shoals of post-larval young of many valuable- 

 demersal fishes. 



There is a method about the detailed distribution of the 

 plankton that convinces one it must depend upon laws or factors 



* See also the connection between Mackerel and Calanus given in 

 this report at p. 52. 



