Coastal currents and the fisheries 477 



important additional conclusions from the relatively complete grids of new stations 



Much improved navigation is of course now available. Underway instruments 

 such as the bathythermograph can now provide much more detailed profiles (about 

 75 such profiles across the continental shelf have been accumulated), but the fact 

 remains that nobody has had the courage to make a sustained attack on the three- 

 dimensional mixing mechanisms going on near the 100 fathom curve. Without the 

 help of entirely new techniques it has seemed too difficult an observational problem, 

 and it has been clear all along that the important clues were to be found in this /one! 



It is a pleasure to be able to announce here that a new programme in coastal cir- 

 culation is being planned at the Woods Hole Oceanographic Institution and has 

 already been set in motion. It has been made possible by funds supplied by the U.S. 

 Fish and WildHfe Service, and made available to the Service by the Saltonstall- 

 Kennedy Act. The present writer is most hopeful that this three-year study will be 

 of real assistance to fisheries biologists, because it is planned to obtain continuous 

 data of various kinds at several key points in the system, as well as to secure some 

 periodic ship surveys. As Ketchum, Redfield and A vers (1951) showed so clearly 

 in their studies of inshore waters off New York, spot observations of tem.peraiurc 

 and salinity can be illuminating if they must also satisfy some continuous require- 

 ment such as the transfer of fresh water through the network of stations. Elsewhere 

 in this volume Dr. Ketchum has attempted to treat the whole continental shelf area 

 from Nantucket to Cape Hatteras as a very wide estuary. This is an important step 

 forward in our thinking, and perhaps all that is needed to refine and to clarify the 

 picture are some long series of current measurements at various depths. 



The new programme will emphasize first of all the more systematic collection of 

 continuous records of temperature and salinity at as many fixed points in the area as 

 possible. The submerged recovery buoy developed by Mr. David H. Frantz at 

 Woods Hole will also be used for temperature observations at some critical points 

 where moored surface buoys cannot be easily maintained. Free floating buoys carry- 

 ing radio transponders will be set out and then located frequently by a plane. Con- 

 tinuous current measurements will be obtained at a number of points, both near the 

 bottom and near the surface. In these ways it is hoped to gain reliable information 

 on how strong and how persistent the winds have to be, to cause a significant dis- 

 turbance in the normal exchange between coastal and ofi"shore waters. 



A recent study by Chase (1955) has indicated that, at least in the case of young 

 haddock, exceptionally prolonged offshore winds during the early spring can be an 

 important factor on Georges Bank. Lacking any current measurements from the 

 waters in which the young haddock float. Chase was forced to use the record of the 

 relative success of the year classes as an indicator of wind-induced currents. His 

 reasoning, while satisfactory to a physical oceanographer, leaves something to be 

 desired from the biological standpoint. A physical oceanographer should be able to 

 state with conviction, on the basis of physical measurements, what the large-scale 

 water movements have been, and then leave it to the biologists to decide whether or 

 not these have had any biological consequences. 



Once the influence of the winds and of the variations in river inflow have been 

 properly assessed, and once the cause and importance of the large-scale mixing 

 processes at the edge of the continental shelf have been worked out, it should be 

 possible to go back over the available data and indicate when and where the coastal 



