Control by Need for Minimum Heat 167 



temperatures are generally lower than 18°C until the Gulf of St. Law- 

 rence is reached where surprisingly warm conditions occur in summer 

 in the shallow areas around Prince Edward Island. Temperatures in 

 the central part of the Bay of Fundy are prevented from rising above 

 11°C by the intense tidal stirring, but the stratified water along the 

 outer coast of Nova Scotia becomes considerably warmer than this. 

 Correlated with these temperature conditions we find that in New 

 England oysters grow naturally in commercial quantities only as far 

 north as Narragansett Bay but "seed" oysters may be transported to 

 Cotuit and elsewhere on Cape Cod, where they are fattened for mar- 



Modified from Ackerman, 1941 



Fig. 5.15. Regions of abundant occurrence of lobsters (small dots) and oysters 

 ( large dots ) in relation to August surface temperatures as indicated by the loca- 

 tion of the commercial catch in 1934. 



ket. Oysters again become sufficiently numerous to market in the 

 littoral zone around Prince Edward Island and in certain warm bays 

 of Cape Breton and northeast New Brunswick. Lobsters, on the 

 other hand, breed successfully in abundance all along the coast of 

 Maine, on the outer coast of Nova Scotia, and into the Gulf of St. 

 Lawrence, but these shellfish are not taken in commercial quantities 

 within the Bay of Fundy. Although lobsters wander into the Bay 

 of Fundy and some of them grow to a large size, the lack of water 



