554 



Fishery Bulletin 93(3), 1995 



lished estimates of growth derived from tagging stud- 

 ies in which similar tagging methods were used. 



Relation of growth to morphology 



The shells of 390 recaptured abalone were retained 

 for further measurement. This allowed us to relate 

 present morphology of the shells to past growth rates. 

 Few shells were retained from Broughton Island I 

 or Eden I because the abalone were used in separate 

 experiments to estimate fishing mortality. Measure- 

 ments taken included the maximum and minimum 

 diameters (length and width), the 

 width of the ventral ridge of the shell 

 at the aboral margin (ridge), and the 

 dry weight of the shell. Relationships 

 among these variables were investi- 

 gated by correlation. To relate present 

 morphology to past growth, the 

 length of all shells was related to 

 their width, weight (log transformed), 

 and ridge by using multiple linear re- 

 gression. The residuals from this re- 

 lationship then indicate whether a 

 shell is longer or shorter than ex- 

 pected given the other morphological 

 variables. In a similar way, all the 

 tagging data were combined into one 

 growth model. The residuals from 

 this growth model then indicate 

 whether an abalone has grown faster 

 or slower than expected. By averag- 

 ing the residuals from the morpho- 

 logical relationship and the growth 

 curve across all individuals at a site, 

 any relationship between rates of 

 growth and shell morphology among 

 sites should be apparent. 



Tagged abalone were at large for a period between 

 8 and 1,736 days, although most (98%) of the indi- 

 viduals were recaptured within two years of release. 

 The range of times between tagging and recapture 

 of abalone differed among sites (Fig. 2B). There were 

 generally shorter times between tagging and recap- 

 ture in Broughton Island I and Sydney I, and longer 

 times at Merrys Beach (Fig. 2B). During the tagging 

 period increments in size ranged from —8 mm to 

 84 mm, with an average of 11.8 mm (SE=0.4). Nega- 

 tive growth may have been caused by erosion of the 

 shell. 



Results 



A total of 1,464 abalone were recov- 

 ered from the seven sites. At tagging, 

 these individuals ranged in size from 

 15 to 152 mm, with a mean size of 

 91.1 mm (SE=0.7). The size of recap- 

 tured abalone at tagging differed 

 among sites. Few of the individuals 

 recaptured at Broughton Island II 

 and Eden I were small when tagged 

 (Fig. 2A). In contrast, few large aba- 

 lone were recaptured from Merrys 

 Beach, both sites in Sydney, and from 

 Eden II. 



c 



u 

 o> 



&, 



>-, 



u 



C 

 01 



3 



cr 



30 



20 



10 







r-nji 1 1 1 n Tru 



Broughton Island I 

 n=124 



30 -i 



20 



10 







30 



20 



10 







i n 4^-f — i — 1 1 1 — \ — * — t— r 



Broughton Island II 



n = m 



^m 



11 



30- 



20- 



10- 







30 

 20 



LD 



tru 



Sydney I 

 n= 113 



Sydney II 

 n = 341 



JX. 



EL 



30 

 20 



10- 

 



r-rfi 



tu 



Merrys Beach 

 n =205 



Eden I 

 n = 377 



30-] 



20 



10 







FFTriT 



Vu- 



Eden II 

 n = \26 



20 40 60 80 100 120 140 160 



Length (mm) 



B 



40 1 



20- 



40 -i 



20- 



nJii 



40-| 



20 



40 



20- 



rn-t-i ,~i 



40-i 



20- 



mrrnn 



40 



20- 







HL 



40-i 



20 







rfHm .., 







12 3 4 

 Time (years) 



Figure 2 



Distribution of (A) length at marking [Y t ) and (B) time at liberty (At) for re- 

 captured blacklip abalone, Haliotis rubra, at seven sites. 



