Hazell et aL: Somatic growth rate of lasus lalandii 



511 



Figure 1 



Map of Table Bay showing the position of the two study sites. Inset: map of 

 southern Africa showing the distribution of rock lobster, Jasus lalandii. 



caused the decline in adult growth rates during the early 

 1990s. A decrease in the size of females at 50% maturity 

 provided indirect evidence that juvenile growth rates may 

 also have been adversely affected (Pollock, 1987; Cockcroft 

 and Goosen, 1995; Pollock, 1995; Pollock, 1997), but this 

 decline in juvenile growth rates has not been confirmed by 

 direct measurement. 



Despite both this substantial gap in our knowledge of 

 the ecology of J. lalandii and the growing international 

 recognition of the importance of understanding the early 

 life history stages of species with complex life cycles 

 I Herrnkind et al. , 1994 ), juvenile growth of this species was 

 last assessed more than 25 years ago ( Pollock, 1973 ). It was 

 therefore essential that juvenile growth be re-examined 

 by repeating Pollock's (1973) study at Cape Town harbor 

 wall. This site was originally selected because of the large 

 numbers of juvenile rock lobster present on the vertical 

 face of the harbor wall and because these lobsters were 

 easy to collect. In our study, a second, natural nursery 

 reef site at nearby Mouille Point (Fig. 1) was selected to 

 compare with the original artificial harbor wall site. 



This paper addresses two hypotheses. The first is that 

 somatic growth rates of juveniles on the harbor wall have 



not declined since Pollock's (1973) study. The second is 

 that juvenile growth rates of rock lobster on the harbor 

 wall are not different from those of rock lobster on the 

 nearby natural nursery reef at Mouille Point. 



Methods 



Juvenile rock lobsters were collected between March 1996 

 and February 1997 at two sites: Cape Town harbor wall 

 (seaward side) and Mouille Point (Fig. 1). Only the harbor 

 wall was sampled in March and intervals between sam- 

 ples were approximately one month, although it was not 

 possible to sample either site every month. Two autumn 

 months (one for Mouille Point), two winter months, two 

 spring months, and three summer months were sampled, 

 thereby allowing for seasonal variation in growth. 



Juvenile rock lobsters were sampled by two SCUBA div- 

 ers who collected specimens for roughly 20-30 minutes, 

 or by one diver for about twice as long (Table 1). At the 

 harbor wall, divers started at the base of the wall (>10 m 

 depth) and worked their way up to the surface, collecting 

 every lobster encountered, where possible. At Mouille 



