332 



Fishery Bulletin 88(2). 1990 



Figure 9 



Variability in the vertical temperature struc- 

 ture at station 64-06 on the Agulhas Bank, 

 southern Benguela Current region. 



S 



32' 



34' 



Position of the surface thermal 

 front, October 1977 to 

 ,0 I. May 1978 



16° 



18- 



20 



22° E 



Figure 10 



Variability in the position of the surface temperature front in the 

 southern Benguela Current region, spring 1977 through autumn 

 1978. (Numbers refer to months of the year, e.g., 10 = October 

 1977, 2 = February 1978.) 



typical for the recruitment area in winter, as shown 

 in Figure 3. 



Robustness to event-scale processes 



Wind stick diagrams of wind strength and direction 

 estimated by the lighthouse keeper at Cape Point (Fig. 

 8) show that winter is characterized by frequent periods 

 of strong northerly wind interspersed with southerly 

 winds and calm, whereas in summer strong upwelling- 

 favorable southeasterlies dominate, alternating with 

 brief periods of calm and occasional wind reversals. 



A SONDJ FMAMJ 

 MONTH 



J A 



Figure 1 1 



Monthly mean abundance of anchovy eggs and larvae over the CELP 

 survey grid, southern Benguela region, for the period August 

 1977-August 1978. 



Despite event-scale forcing of this nature, contoured 

 monthly temperature profiles through the water col- 

 umn over the Agulhas Bank show strong stratification 

 persisting over several months of the spring-to-autumn 

 period, weakening and disappearing with the onset of 

 winter (Fig. 9). Similarly, although erratic in appear- 

 ance and position to the north and south, the tempera- 

 ture front in the transport area between Cape Point 

 and Cape Columbine persists as a stable feature for up 

 to 8 months of the year (Fig. 10), despite event-scale 

 variability in the wind field. During lulls in upwelling 

 the front may weaken at the surface and move inshore, 

 at which time the temperature discontinuity may be 

 most apparent in the form of a thermocline, but it per- 

 sists as a subsurface feature further offshore (Shelton 



