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Fishery Bulletin 93(3), 1995 



was not conserving enough egg production (Hamer, 

 1983). In response, the minimum legal length limit 

 was increased in a series of increments from 100 mm 

 in 1979 to 115 mm in 1987. An unfortunate conse- 

 quence of these increases was the concentration of 

 fishing effort at sites where abalone grew quickly and 

 to large sizes (see also McShane, 1992). Because of 

 this high level of effort and the limited dispersal of 

 larval abalone (Prince et al., 1987), such sites were 

 often overexploited, whereas in other areas where 

 abalone grew more slowly to smaller sizes the popu- 

 lations were underexploited. 



In this study, we describe a tagging study of varia- 

 tion in the growth of Haliotis rubra at seven sites 

 along the NSW coast. These sites were grouped into 

 four locations encompassing most of the geographi- 

 cal range of the fishery. This provides an indication of 

 the variability in growth of the species at three spatial 

 scales: among locations separated by hundreds of km, 

 among sites separated by 1-20 km, and among indi- 

 vidual abalone within the sites. In addition we describe 

 morphological differences among the abalone that ap- 

 pear to be related to their rate of growth. This link be- 

 tween growth and morphology suggests that a mini- 

 mum legal width limit may be more appropriate than 

 the present size limit based on length. 



curve for all recaptured individuals and in the rela- 

 tionship among morphological variables (see below). 

 Small (=2 x 10 mm), numbered plastic tags were 

 attached to abalone with a cyano-acrylate glue be- 

 tween 20 May 1975 and 3 October 1981. This proce- 

 dure required that abalone be removed from the 

 water and their shells dried with compressed air 

 before tagging. Individuals were chosen to make the 

 size range at tagging representative of the popula- 

 tion at each site. The maximum diameter (i.e. length) 

 of each shell was measured to the nearest 0.5 mm, 

 and the abalone were then replaced in the area near 

 where they were collected. Samples of these tagged 

 abalone were recaptured at opportunistic times be- 

 tween 11 December 1975 and 18 May 1982. 



Patterns in growth 



Estimates of growth were obtained by using proce- 

 dures based on a mark-recapture analogue of 

 Schnute's ( 1981) general growth model (see Francis, 

 in press). Schnute's model relates size to age by sev- 

 eral parameters, including two (o and b) which com- 

 bine to describe a range of traditional growth curves 

 including the von Bertalanffy (a > 0, b = 1), Richards 



Materials and methods 



Sites and tags used 



Abalone were tagged at seven sites, 

 spanning almost 1,000 km of coastline, 

 that were chosen because they were 

 commonly used by commercial divers in 

 the NSW abalone fishery (Fig. 1). Six of 

 the sites were grouped into three loca- 

 tions (Broughton Island, Sydney, and 

 Eden) each with two sites (referred to 

 as I and II) separated by between 1 and 

 20 km. The single site at Merrys Beach 

 was approximately midway between 

 those at Sydney and Eden (Fig. 1). 

 Supplementary tagging was also done 

 at Bittangabee Bay near Eden (Fig. 1). 

 This site was not commonly used by 

 commercial fishermen because few in- 

 dividuals reached lengths above the 

 115-mm minimum legal limit. Esti- 

 mates of growth parameters for Bittan- 

 gabee Bay were not calculated sepa- 

 rately because only 20 individuals were 

 recaptured. These abalone were, how- 

 ever, used in the estimation of a growth 



150 E 



35 S 



Broughton Island 



j£> 



5km 



Figure 1 



Map of Australia (inset) and New South Wales (NSW), showing the posi- 

 tion of eight sites within four locations where blacklip abalone, Haliotis 

 rubra, were tagged. Sites I and II within each location are as indicated on 

 the maps; BB = Bittangabee Bay, MB = Merrys Beach. 



