THE SMALL GAME OF THE SEA 193 



difference between wholesale destruction of the brood and an 

 abnormally large hatch of herring, cod, and haddock. A newly 

 hatched plaice in an aquarium has been observed feeding on 

 a diatomic plant called Navicula which was growing at the 

 ])ottom of the glass tank. 



The diatoms are, however, equally important because they 

 undoubtedly furnish the food of the ' small game ' on which 

 fish feed. And Dr. Lebour has proved that httle herring and 

 other babies take to eating the larvae of certain molluscs and 

 small crustaceans before the yolk has all gone. It is here 

 possible only to compile quite a few notes about these small 

 animals. 



By far the greater part of the food of very young fish consists 

 of the larvae of certain Crustacea called Copepods or 'Oar Jeet\ 

 These — in water north of the Bay of Biscay — consist of between 

 forty and fifty different species. They are never more than 

 a few millimetres in length, and they live on the small plants 

 which float at the surface. The illustration (Plate XX) shows 

 a typical form which is eaten largely by young cod and also 

 by ' finner ' whales. This particular species, according to Gran 

 and Damas, breeds in the spring above the Continental slopes 

 of the Norwegian Sea. The young go through five larval stages, 

 and only assume the shape of the adult in the sixth. The same 

 men who have worked out the life-history of the cod have 

 worked out that of Calanus, and they have been equally enthusi- 

 astic about each. This — the writer has heard it over and over 

 again — has been accounted unto them for unrighteousness. It 

 is almost incredible that such an ignorant view should be so 

 generally held in 1920, but has Science explained ? 



The Calani, Hjort tells us, ' constitute the main nourish- 

 ment upon which, more or less directly, the animal life of the 

 Norwegian Sea depends ; ' they are supposed each to eat 

 almost one-tenth of their own weight in microscopic floating 

 plants every day. Off Plymouth, at any rate, Dr. Lebour is 

 convinced that copepods form the chief food of larval and post- 

 larval fish ; and by far the greater number of fish eat the species 

 which is depicted in Plate XX either in one of its larval stages or 

 in the adult stage — and three other species whose names are in 

 the foot -note. 1 In the Norwegian Sea Calanus practically dis- 

 appears in ^^^nter, but off Plymouth the four species named 



^ Pseudocalanus elongatus, Acartin claiisi, Temma longicornis. The most 

 important copepod in the North-east Atlantic is the open water species Calanus 

 finmarchicus. But Temora is a favourite food of some fish. For instance, in 

 January 1872 Kiel harbour was crammed with herrings for three weeks, and 

 each herring was crammed with a compact pink bolus consisting of about 

 60,000 Temorae. 



2497 N 



