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Fishery Bulletin 100(3) 



1996-97 than those recorded in 1971-72 (Pollock, 1973), 

 irrespective of size. Although corresponding measures of 

 intermolt period are not available, established trends in 

 juvenile rock lobster biology indicate that such data would 

 probably not have exhibited conflicting trends. In general, 

 their growth rates tend to respond first by changes in 

 molt frequency and then, under more extreme conditions, 

 by changes in molt increments (Chittleborough, 1975; 

 Serfling and Ford, 1975; Philhps et al., 1977; Dennis et al., 

 1997). Therefore, the trend to smaller growth increments 

 among juvenile J. lalandii at the Cape Town harbor 

 wall between 1971-72 and 1996-97 was most plausibly 

 accompanied by an increase in intermolt period. 



Adding credence to this deduction are Cockcroft and 

 Goosen's (1995) results, which demonstrated that the 

 size at which female J. lalandii reach sexual maturity 

 on a range of fishing grounds had decreased significantly 

 over the two decades leading up to the mid-1990s. Using 

 simulation models, Pollock (1987) demonstrated that 

 reduced juvenile growth rates would lead to a smaller 

 size at sexual maturity. In combination, these conclusions 



provided additional rationale for rejecting the hypothesis 

 that somatic growth rates of juvenile J. lalandii on the 

 harbor wall have not declined since the last study. 



Pollock (1973) found that a modal size of 38 mm CL was 

 attained approximately 1.6 years after settling. This alone 

 implies a slower growth rate than that for other temperate 

 lobster species (Jernakoff et al., 1994). Because our data 

 suggest that current growth rates are even slower than this, 

 and that they may decline further with falling adult growth 

 rates, recruitment to the fishable part of the J. lalandii 

 resource must be seen as a real management concern 

 (Bergh and Johnston, 1992). Therefore, the precautionary 

 assumption made in the operational management pro- 

 cedure designed for this resource (Cockcroft and Payne, 

 1999; Pollock et al., 2000) that juvenile growth mirrors 

 adult growth is justified. 



Another feature of trends in growth rates shared be- 

 tween adult and juvenile J. lalandii is small-scale spatial 

 variation. During the monitoring period, juveniles of 

 this species grew relatively faster at Mouille Point than 

 at the harbor wall, both in terms of molt increment 



