Paper 12 



WIND DRIVEN TRANSPORT 

 ATLANTIC COAST AND GULF OF MEXICO 



Merton C . Ingh am 



INTRODUCTION 



Variations in surface currents and transports resulting from 

 changes in the overlying wind field are significant factors in 

 the survival and development of the early stages of several 

 resource species and the strength of year classes of their 

 populations. This is especially true for species whose larvae 

 spend a relatively lonq period of time as plankton in the surface 

 layer. 



An example of the influence of wind driven transport on larval 

 survivals recruitments and year class strength can be found in 

 the Atlantic menhaden. Winter spawning of this species takes 

 place south of Cape Hatteras at some distance offshore^ near the 

 edge of the Gulf Stream. Eggs and larvae from this spawning 

 activity are transported toward estuarine nursery grounds/ under 

 favorable conaitions/ by wind driven currents in the surface 

 layer. Studies of monthly Ekman (wind-driven) transport and 

 recruitment for the years 1955-70 have revealed a strong link 

 between years of high or low recruitment and years of strong or 

 weak westward Ekman transport during January-March. A model 

 relating these factors shows that variations in January-March 

 zonal Ekman transport at a point south of Cape Hatteras accounts 

 for about 60% of the variation between actual and expected 

 (density-dependent) recruitment (Nelson et al. 1977). 



In addition to the effect of «/ind driven transports on larval 

 drift/ there are other reasons for scientific interest in the 

 variations of Ekrran transport: 



'Atlantic Environmental Group/ National 

 Service/ NOAA/ N a r ragnase 1 1 / RI OeLbbd. 



Marine 



Fisheries 



175 



