Griffiths. Life history and stock separation of silver kob, Argyrosomus inodorus 
61 
Length class (5 cm) 
Figure 1 2 
Regional total-length distributions of Argyrosomus inodorus 1) 
landed by the South African line fishery, 1990-94 (hatched lines) 
and 2) caught on linefish grounds during experimental fishing 
operations and which were below the minimum size limit (40 cm) 
(shaded area). Arrows indicate female median length at matu- 
rity (L 50 ). L 50 was not estimated for the southwestern Cape. 
intermediate zone. During spring, summer, and au- 
tumn, the intermediate zone is restricted to an area 
within a few kilometres of the coast and is within 
easy range of line boats (see 50-m isobath in Fig. 1). 
In winter the bottom mixed layer retreats down the 
shelf to about 100 m (Schumann and Beekman, 1984; 
Eagle and Orren, 1985; Swart and Largier, 1987). 
As the intermediate zone expands, I propose that A. 
inodorus stocks disperse seaward, moving beyond the 
grounds of the linefishery and onto the inshore trawl- 
ing grounds. Because Agulhas Bank is much nar- 
rower in the southeastern Cape than in the south- 
ern Cape (Fig. 1), offshore movement would have 
been more constrained than in the latter region and 
hence would explain the higher winter line catches 
in the southeastern Cape (Fig. 5). 
Owing to a higher degree of coastal upwelling off 
the southwestern Cape, the bottom mixed layer 
