PLANKTON OP THE GULF OF MAINE 167 



The distribution of these and of other warm-water planktonic animals is dis- 

 cussed in a preceding chapter (p. 53). 



Copepods 



Except in certain restricted localities, or for brief periods when some other 

 animal swarms, the animal plankton of the Gulf of Maine consists chiefly of copepods 

 at all seasons. The seasonal fluctuations of the group as a whole are touched on 

 above. The following chapter gives brief discussions of most of the species so far 

 detected in the plankton of the open gulf or at St. Andrews (Doctor McMurrich's 

 lists, p. 12). The great majority are forms that are not only typically pelagic but 

 widespread in northern seas; but at St. Andrews, where strong tides stir the water 

 from bottom to top, sundry dwellers in the littoral zone are brought up to or near 

 the surface, and probably this takes place more or less in estuarine situations all 

 around the shore line of the gulf. Samples of the copepods collected in 1912, 1913, 

 and 1914 were identified by Dr. C. O. Esterly, and lists for those years have been 

 published elsewhere (Bigelow, 1914, p. 115; 1914a, p. 409; 1915, p. 287; 1917, 

 p. 290). It is not necessary to repeat them here. Only a preliminary survey has 

 been made of the copepods towed by the Grampus in 1916 (Bigelow, 1922), but 

 Dr. C. B. Wilson has supplied lists for the vertical hauls made in 1915 and the spring 

 of 1920 and for the horizontals for the winter of 1920-21, which are tabulated 

 below (p. 297). Doctor McMurrich's manuscript lists of plankton for St. Andrews, 

 New Brunswick, have been especially instructive for the seasonal periodicity of 

 the copepods. 



Previous to the inception of the Grampus cruises in 1912, almost no attention 

 had been paid to the copepods of the Gulf of Maine, the only published data for 

 that precise region being a few notes on species from Plymouth Harbor, Mass. 

 (Wheeler, 1901). Subsequently Willey (1919, 1920, and 1921) has given some 

 notes on the copepods of the St. Andrews region in the Bay of Fundy. The Copepoda 

 of southern New England have been studied by Wheeler (1901), Williams (1906 

 and 1907), Sharpe (1911), and Fish (1925) ; those of the outer coasts of Nova Scotia 

 and of the Gulf of St. Lawrence by Herdman, Thompson, and Scott (1S98), by T. 

 Scott (1905), and by Willey (1919), whose lists of the species collected by the Cana- 

 dian fisheries expedition of 1915 are referred to repeatedly in the following accounts 

 of the several species. 



All living copepods are small — the largest up to 10 to 11 millimeters, the smallest 

 less than 1 millimeter in length. The commonest Gulf of Maine species (Calanus 

 finmarchicus) is about 2 to 5 millimeters long when adult. They are present in such 

 immense numbers in the plankton, and they reproduce so rapidly, that they are the 

 most important of all pelagic invertebrates from the economic viewpoint, furnishing 

 the primary food for the young of most marine fishes until these attain considerable 

 size, as well as for many of the larger planktonic animals of various groups. Copepods 

 are the major article in the diet of the adults of such plankton-feeding species as the 

 mackerel and all the herring tribe. This aspect of copepod economy is touched 

 on in another chapter (p. 97). I need only emphasize here that evidence is con- 

 stantly accumulating to prove that the fertility of any part of the northern seas in 



