Worthington et al.: Alternative size limits for Hahotis rubra in New South Wales, Australia 



555 



Patterns in growth 



The shape of the fitted growth curve differed signifi- 

 cantly among sites U-tests, P<0.05; Table 1). At 

 Broughton Island I and Sydney I, the fitted growth 

 curve was similar to a traditional von Bertalanffy 

 shape (a > 0, b = 1 in Table 1), whereas at Eden II it 

 was more similar to a Gompertz shape (a > 0, b ~ 

 in Table 1 ), and at Merrys Beach more similar to a 

 logistic shape (a > 0, b = -1 in Table 1). All curves 

 were asymptotic and expected growth approached 

 zero (Fig. 3B). The size at which expected growth 

 equalled zero differed among sites and ranged from 

 118 mm at Merrys Beach to 151 mm at Broughton 

 Island II (Fig. 3B; Table 1). 



Estimates of average annual growth rates differed 

 significantly among the seven sites (Table 1). Aba- 

 lone at the two sites on Broughton Island had faster 

 rates of growth than all other sites. At Broughton 

 Island II a 65-mm abalone was 

 expected to grow to the 115-mm 

 length limit in approximately 18 

 months (Fig. 3A). Above 115 mm, 

 growth declined rapidly so that in 

 the next year expected growth was 

 less than 10 mm. The rate of de- 

 cline in growth rate then slowed, 

 and growth was expected to con- 

 tinue until 151 mm (Fig. 3; Table 

 1). In contrast, growth at Sydney 

 I was much slower; a 65-mm indi- 

 vidual was expected to take almost 

 9 years to grow to 115 mm (Fig. 3A). 

 Growth rate declined at an approxi- 

 mately constant rate throughout life 

 (i.e. approximating a von Bert- 

 alanffy growth curve) until indi- 

 viduals were expected to have no 

 growth at 126 mm (Fig. 3; Table 

 1 ). At Merrys Beach, abalone were 

 expected to grow from 65 mm to 

 90 mm within a year, but then 

 growth declined rapidly and indi- 

 viduals were expected to grow only 

 just above the minimum length 

 limit of 115 mm (Fig. 3A). Growth 

 rates at Sydney II and Eden II 

 were not significantly different at 

 any of the standard sizes (Table 1). 



There was significant variation 

 in growth among individual aba- 

 lone within all sites (Table 1). 

 Variation in growth among aba- 

 lone at Merrys Beach was signifi- 

 cantly less than that at all other 



sites and significantly greater at Broughton Island 

 II, Sydney I, and Eden I U-tests, P<0.05). The stan- 

 dard deviation of the observed growth increment 

 ranged from 0.29 times the expected increment at 

 Merrys Beach to 0.87 times the expected increment 

 at Eden I (Table 1). This range implies that two-thirds 

 of the abalone at Merrys Beach will grow between 

 0.71 and 1.29 times the expected increment, whereas 

 at Eden I, two-thirds of the abalone will grow be- 

 tween 0.13 and 1.87 times the expected increment 

 (Fig. 4). 



Parameters representing seasonal variation in 

 rates of growth significantly improved the fit of the 

 model at three of the seven sites (Table 1). At 

 Broughton Island II, peak growth rates occurred 

 during late October at 1.9 times the minimum growth 

 rate in late April. In contrast, peak growth rates at 

 both Sydney II and Eden I occurred in December at 

 a rate 2.0 and 2.9 times the minimum, respectively 



2 4 6 



Time (years) 



2 4 6 



Time (years) 



10 



B 



i>) 



20 40 60 80 100 120 140 

 Length (mm) 



50 



30 



10 







-10 



20 40 60 80 100 120 140 

 Length (mm) 



Figure 3 



Predicted mean growth of blacklip abalone, Haliotis rubra; (A) over 10 years for 

 individuals of a given size and (B) over 1 year for individuals of a range of sizes. 

 Growth is shown from (i) 40 mm at sites where many small abalone were tagged 

 and (ii) 65 mm at sites where few small abalone were tagged up to the size of the 

 largest abalone. Sites are abbreviated as follows: BI and BII = Broughton Island I 

 and II; SI and SII = Sydney I and II; MB = Merrys Beach; EI and EII = Eden I and II. 



