PELAGIC COMMUNITIES 321 



gators and summarized by him bring out some features of dominance 

 in pelagic communities in connection with the whales. The whale- 

 bone whales are the largest constituents of the biome in the Gulf of 

 Maine; their food consists of copepods and euphausiids (schizopods), 

 supplemented with fishes. In the long run the crustaceans are appar- 

 ently of greatest importance in most cases (Brooks, 1893; Clark, 1933 

 a, b, 1936). The food is strained from the water by whales and by 

 some fishes also, and Bigelow stresses the fact that the finer strainers 

 are better adapted to the catching of small forms, and less effective in 

 catching fishes, etc. 



Bigelow further points out tendencies for particular consuments to 

 seek certain types of plankton or nekton. The menhaden feeds on 

 the unicellular algae (chiefly diatoms) throughout life. Copepods also 

 feed on diatoms, and some other fishes subsist chiefly on Crustacea, 

 chiefly copepods. Sagitta appears more important in reducing cope- 

 pod numbers than fishes. These crustaceans are present in reduced 

 number where Sagitta is abundant. He also states that certain cteno- 

 phores take nearly all living things that come in contact with them. 

 Wherever these creatures abound, most of the small animals tend to 

 be extirpated. On the other hand, ctenophores, themselves, are not 

 eaten by larger animals. 



The character of dominance, or in other words the control of the 

 community by organisms, is puzzling. One may, however, venture 

 to suggest that dominance by the copepod, Calanus finmarchicus, is 

 indicated in the Gulf of Maine. It is present in outstanding quan- 

 tity, being able to replace population losses so rapidly as to supply 

 the greater part of the food for fishes and many other forms both large 

 and small. It is thereby assimied to serve as the basis for much of 

 the pelagic life of the bay (cf. Brooks, 1893). Again the menhaden 

 may also be regarded as an important dominant because of its ability 

 to utilize diatoms, as well as by reason of its great abundance. 



The wide distribution of the microscopic plants and the small ani- 

 mals that make up the smallest constituents of plankton, and the 

 relatively non-selective manner in which they are taken by important 

 dominant organisms such as Calanus, hardly puts them in the dom- 

 inant class. They are, however, of fundamental importance as the 

 basis of the food supply of the entire group of pelagic biomes, and 

 constitute a sort of universal mass of food materials for such large 

 crustaceans, mollusks, fishes, etc., as probably may properly be con- 

 sidered as the dominants of pelagic communities. 



The bathysphere observations of Beebe (1930, 1932, a, b) indicate 

 that pelagic animals are far more numerous than was formerly sup- 



