478 C. O'D. ISELIN 



environment was seriously disturbed. The biologists are by no means satisfied that 

 environmental changes of sufficient magnitude have occurred to account for the 

 goings and comings of fish. It is the aim of the new programme to find means of 

 setthng this matter one way or another. Even if it only serves to bring the circulation 

 problem into closer contact with biological needs, an important step forward will 

 have been taken. 



To summarize the present situation in coastal oceanography, our basic problems 

 can be set forth as follows: 



(1) The available data are inadequate to establish how variable the coastal environ- 

 ment may be because of fluctuations in its principal energy source, namely land 

 drainage, 



(2) So far as the oceanic currents are concerned, it is beheved that the winds, 

 either directly or indirectly, supply most of the energy. Considerable variations in the 

 offshore currents are known to exist, but to what degree these influence the inshore 

 currents remains obscure, 



(3) Coastal currents, on the other hand, for the most part operate without the 

 direct help of the winds, yet strong and prolonged winds could be a cause of im- 

 portant variations in the environment from the biological standpoint, especially 

 for fishes which spawn near the edge of the continental shelf, 



(4) Occasional surveys of the distribution of temperature and salinity are unlikely 

 to provide more than limited understanding of the coastal currents, for the classical 

 theories of physical oceanography assume steady-state conditions and, because of 

 tidal currents, this simplification is far from being justified in coastal waters. 



(5) Continuous observations, even of a rather simple sort at well-selected points 

 over the continental shelf, should provide means of evaluating the influences of varia- 

 tions in river inflow, of the local winds, and of the off'shore currents. Fortunately, 

 new means of obtaining such observations have been developed in recent years. 



(6) Once these factors have been evaluated, the major environmental fluctuations 

 can probably be deduced as far back as the weather record extends. 



(7) The general distribution of temperature and sahnity in coastal waters indicates 

 that, except briefly in mid-winter, it operates as a three-layered system. The warm 

 wind-stirred surface layer and the cold stable layer just below both have off'shore 

 components, but probably quite different ones. Near the bottom, and especially 

 where guUies and drowned river valleys exist, there is an inshore component. By 

 moving up or down in the water column an organism can be carried either inshore or 

 off'shore. By the large-scale interaction of coastal and oceanic water it can either be 

 carried up-coast or down-coast. From the biological standpoint it is important to 

 estabhsh how steady or how variable these current systems may be. 



REFERENCES 

 BiGELOw, H. B. (1927), Physical oceanography of the Gulf of Maine. Bull. U.S. Bur. Fish., 40 (2), 



511-1027. 

 BiGELOW, H. B. (1933), Studies of the waters on the continental shelf, Cape Cod to Chesapeake Bay. 



1. The cycle of temperature. Pap. Phys. Oceanogr. Meteorol., 2 (4). 

 Chase, Joseph (1955), Winds and temperatures in relation to the brood strength of Georges Bank 



haddock. J. du Cons., (in press). 

 FuGLiSTER, F. C. (1955), Alternative analyses of current systems. Deep-Sea Res., 2, 213-229. 

 Ketchum, B. H. and Keen, D. J. (1955), The accumulation of river water over the continental shelf 



between Cape Cod and Chesapeake Bay. Pap. Mar. Biol, and Oceanogr., Deep-Sea Res., SuppL, 3. 

 Ketchum, B. K., Redfield, A. C. and Ayers, J. C. (1951), The oceanography of the New York 



Bight. Pap. Phys. Oceanogr. Meteorol., 12 (1), 1-46. 



