MARINE BIOLOGICAL STATION AT PORT ERIN. 69 



Diatoms, Dinoflagellates and Protozoa. So practically all the 

 main constituents of the plankton are concerned in the nourish- 

 ment of either young or adult fishes. On the Lancashire coast 

 we find the young plaice which are just appearing in the inshore 

 nurseries have their stomachs filled with pelagic larval annelids. 



The Pollan (Coregonus pollari) of Lough Neagh, in Ireland, 

 has been shown to be on some occasions filled up with My sis 

 relicta, and at other times to be feeding solely on Cladocera ; 

 and there is reason to believe that the movements of the fish, 

 which are extensive and periodic, can be definitely related to 

 the presence and nature of the plankton. 



Dr. Hjort has shown a correspondence between the 

 distribution of the plankton-feeding whales (such as the 

 Greenland whale) and the most abundant swarms of plankton 

 at particular seasons. Professor G. 0. Sars and others, in 

 tracing shoals of herring and cod in the North and West of 

 Norway, have distinguished between the " feeding " migrations 

 and the spawning migrations, and the feeding migrations depend 

 upon the plankton. 



It seems, probable that, in order to get an adequate 

 quantity of planktonic food the fish, in most cases, must seek 

 out and capture the Copepoda, for example, just as fish on 

 occasions have been seen to do. In other words, the fish must 

 go where the plankton is abundant, and must in its migrations 

 follow the movements of shoals of plankton. It is the very 

 poverty of the plankton in some sea areas, insisted on by 

 Piitter, Lohmann and others, which makes it necessary for 

 plankton- eating fish to move about in search of more abundant 

 supplies. 



This association of shoals of fish with abundance of 

 plankton is in agreement with many observations that have 

 been made by naturalists in the past. It is well known that in 

 coastal waters favourite line-fishing localities are usually where 

 strong tides run through narrow channels or over rocks and 



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