In this summary (Table 1) we have treated the 

 Gulf of Maine and the Middle Atlantic Bight sepa- 

 rately for there is an abrupt general division be- 

 tween the biological and physical properties of 

 water east and west of Cape Cod. The boreal wa- 

 ters over most of the Gulf of Maine are well mixed 

 by strong tidal currents, while the circulation of 

 the warmer shelf waters west of Cape Cod is more 

 sluggish, and its chemical and physical properties 

 are less complex (Colton 1964). The offing of Cape 

 Cod also appears to be a definite transition zone 



(probably thermal) for some northern and south- 

 ern species of fishes and invertebrates, both 

 pelagic and benthic (Colton 1964). The species 

 composition and abundance of fishes vary marked- 

 ly between the two regions, with boreal, non- 

 migratory species dominating the Gulf of Maine 

 and warmwater, migratory species prevailing in 

 the Middle Atlantic Bight. The bulk or total 

 spawning of many species of fishes is restricted to 

 areas east (e.g., haddock, pollock, redfish) or west 

 (e.g., bluefish, menhaden, anchovies) of Nantuck- 



Table 1. — Principal spawning areas and times of marine fishes. Cape Sable to Cape Hatteras. 



913 



