60 
Fishery Bulletin 95(1 J, 1997 
EL PA MB SSB FB 
Nov-91 Oct/Nov-91 Oct-91 Oct-91 Oct-91 
Males 
m Stage 7 
■ Stage 6 
□ Stage 5 
□ Stage 4 
a Stage 3 
□ Stage 2 
EL PA MB SSB FB 
Nov-91 Oct/Nov-91 Oct-91 Oct-91 Oct-91 
Sampling site 
Figure 1 1 
Percentage of gonad stages observed for male and female Argyrosom us inodorus 
at five localities during the peak spawning season in 1991. EL=East London, 
PA=Port Alfred, MB=Mossel Bay, SSB= St Sebastian Bay, FB=False Bay, and 
n=sample size. Fish sampled at the first four localities were caught by hook 
and line, whereas those in False Bay were caught with beach-seine nets. 
ited exchange between the southwestern Cape and the 
southern Cape stocks but that there is no exchange 
between either of these two stocks and the one in the 
southeastern Cape. Analysis of catch and tagging data 
shows that each of the three stocks is concentrated in- 
shore in summer but disperses seawards in winter. 
The distribution of silver kob on the South African 
eastern seaboard, including the existence of the three 
stocks and their onshore-offshore movement, is also 
supported by regional oceanographic patterns. Dur- 
ing spring, summer, and autumn, the east coast be- 
tween Cape Agulhas and the Kei River is character- 
ized by three zones: 1) a warm inshore band (0-20 
m) with an average temperature of 21°C (although 
in certain areas temperatures can drop to <12°C for 
brief periods following coastal upwelling); 2) a zone 
of intermediate temperature (12-19°C) between 20 
and 50 m; and 3) a bottom mixed layer of <12°C found 
below 50 m (Eagle and Orren, 1985; Swart and 
Largier, 1987; Goschen and Schumann, 1988; Boyd 
and Shillington, 1994; Greenwood and Taunton- 
Clark 2 ). Silver kob prefer temperatures of 13-16°C 
(Fig. 14) and are therefore mainly confined to the 
2 Greenwood, C., and J. Taunton-Clark. 1992. An atlas of mean 
monthly and yearly average sea surface temperatures around 
the southern African coast. Sea Fisheries Research Institute, 
Private BagX2, Roggebaai 8012, Cape Town, South Africa. In- 
ternal report 124, 112 p. 
