172 BULLETIN OF THE BUREAU OF FISHERIES. 



liyder (ISSl) sa^'s that the food of youiiy- .-^had consists almost entirely of very 

 small crustaceans, in reality for the most part Daphnidse and Lviiceida\ In speaking 

 of the adult shad, he states that he found a large quantity of a copepod, a^iparently 

 a ('i/cl(>j)n, in the stomach of a spawning female. He says that there were prohalily 

 a liiindred thousand of these copepods in the stomach. 



Brook (1887) found that very .young cod and saith fed almost entirely on copepods. 

 Brook and Calderwood (1886) state that copepods supply the principal food of the 

 herring during the summer months, and ostracods were found occasionally. 



Fric and Vavra (18!»4 and I'JOl) found plankton Crustacea in the stomachs of 

 several species of fresh- water tishes. 



Herdman (1894) states that hy far the most injpt)rtant constituent of the food of 

 young \)\-Ki\i-e{Ph'ur(int'ct''ii /ih(ti.'<xa) seems to be the Harpacticidi^?, especially the species 

 Jt>ne»!dla }u/:v»n'. Records foi' nearly 900 specimens show that sizes of about an 

 inch ('2.5 centimeters) in length live mainly on Copepoda. He also found that cope- 

 pods form a part of the food of specimens 3 inches (7.5 centimeters) or more in 

 length. Herdman and A. Scott (1895) state that after the larval marine tishes which 

 they studied have absorbed the food supply stored up in the yolk-sac they pass to 

 the stage in which copepods form their chief food. In his investigations on Lake 

 St. Clair, Reighard (1894) found that Daphnida- and Copepoda were eaten by variou.s 

 fish larva" and the lake herring. Peck (1894 and 1896) found ostracods in the stom- 

 achs of menhaden and copepods in the stomach of a scup. In speaking of his investi- 

 gations on the Great Lakes, Ward (1896) .says that the smaller forms of crustaceans 

 are eaten by the fish fi'y directly, and are sometimes the immediate food of the 

 larger fishes. 



Walter (1895-1899) obtained some interesting results in this respect in his studies 

 of the food of fishes. I have not seen his own statements concerning these results, 

 but Steuer (IDOl) says the following of them: "'Nach den Untersuchungen E. 

 Walter's konnen wir den Satz aufstellen, dass ganz allgemein die Menge des vor- 

 handenen thierischen Planktons direkt proportional ist d(>r Menge der in dem Teiche 

 iiberhaupt vorhandenen Fischnahrung. Die Gesammtproduction an thierischen 

 Plankton steht somit in geradem Verhaltniss zum Zuwachs der Fische, d. h. je mehr 

 Plankton, desto grosser der Zuwachs, je weniger Plankton, desto geringer der 

 Zuwachs." 



In describing an observation made on Lake Mendota, Wisconsin. Birge (1897) 

 says that "The surface water was crowded with Daphnla, and an immense numlier of 

 perch were feeding on them." 



Scourfield (18H8) states that three specimens of the three-spined stickleback 

 {GaxtcroHteii8 iiciih'atiiK) imd three roach {Lfaeisras rati lux) which he examined had 

 been feeding extensively on several forms of Entomostraca. lluitfeldt-Kaas (1898) 

 found 50,n(i0 Boxinina in the stomach of a Coregvnus lavaretus. He says that 

 Bi/tliurej/tex Inmjimanus was the usual species found in the stomachs of trout and 

 (^iirego)nix^ and next came Bosmlna vhtuxirosfrix and Daplinla galeata. 



Nordgaard (1900) sa3-s that Culanxmfinmarchic^ix constitutes the main part of the 

 food of the herring along the coast of Norway, and also (1905) that the ostracod 

 L'ljpi'hlinit ii(irrr(jic<i was found to t'onstitute part of the food of the cod {Gadtis 

 calliiriiix). 



