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Fishery Bulletin 103(4) 



mine optimal parameterization of models (Kimura, 1980; 

 Francis, 1988a). Computationally intensive methods 

 such as bootstrapping and randomization tests provide 

 a nonparametric method for approximating probability 

 distributions of growth parameter estimates (Haddon, 

 2001), for generating confidence intervals to test for 

 differences between parameter estimates, and for visu- 

 alizing relationships between parameters (Mooij, et al., 

 1999). Drawing together these methods, it is possible to 

 fit growth models, to produce parameter estimates that 

 are biologically interpretable, and to use tests that are 

 robust for comparing populations. 



The purple wrasse (Notolabrus fucicola) is a gono- 

 choristic, site-attached, reef-associated fish, common on 

 moderate to fully exposed coasts in southeastern Aus- 

 tralia and New Zealand (Russell, 1988; Edgar, 1997). 

 Both Notolabrus fucicola and its Australian congener, 

 the blue-throated wrasse (N. tetricus), are large benthic 

 carnivores that play a significant role in the trophic 

 dynamics of temperate reef systems (Denny and Schiel, 

 2001; Shepherd and Clarkson, 2001). 



The development of a live fishery for N. fucicola and 

 N. tetricus in southeastern Australia has made temper- 

 ate wrasses increasingly important economically (Lyle 1 ; 

 Smith, et al. 2 ). 



Most previous attempts to describe the growth of 

 N. fucicola (Barrett, 1995a; 1999; Smith, et al. 2 ) have 

 been compromised by small sample sizes, lack of age 

 validation, and the use of unsuitable statistical models 

 to compare length-at-age between populations. Ewing et 

 al. (2003) recently validated an aging method and devel- 

 oped growth models for JV. fucicola, combining samples 

 from many sites from eastern and southeastern Tasma- 

 nia. Our study describes site- and sex-specific age- and 

 length-based models for this species. We also compare 

 methods for examining differences in growth model 

 parameter estimates, such as confidence intervals and 

 randomization tests based on bootstrap estimates, plots 

 of bootstrap estimates, and LRTs where comprehensive 

 coverage of age and length data is unavailable — a situ- 

 ation commonly faced in fisheries. 



Materials and methods 



Field methods 



Notolabrus fucicola were trapped and tagged at two sites 

 on the east coast of Tasmania. Trapping was conducted 



1 Lyle, J. M. 2003. Tasmanian scalefish fishery— 2002. Fish- 

 ery Assessment Report, 70 p. Tasmanian Aquaculture and 

 Fisheries Institute, Marine Research Laboratories, Univ. Tas- 

 mania, Nubeena Crescent, Taroona, Tasmania 7053, Australia. 



- Smith, D. C, I. Montgomery, K. P. Sivakumaran, K. Krusic- 

 Golub, K. Smith, and R. Hodge. 2003. The fisheries biol- 

 ogy of bluethroat wrasse (Notolabrus tetricus) in Victorian 

 waters. Draft Final Report, Fisheries Research and Devel- 

 opment Corporation No. 97/128, 88 p. Marine and Freshwa- 

 ter Resources Institute, 2a Bellarine Highway, Queenscliff, 

 Victoria 3225, Australia. 



at 1-2 month intervals, between July 1999 and April 

 2001 at Lord's Bluff (42. 53°S, 147.98°E), and between 

 July 2000 and March 2001 at Point Bailey (42.36°S, 

 148.02°E). Standard T-bar tags were inserted between 

 the pterygiophores in the rear portion of the dorsal fin. 

 Total length of each fish was recorded prior to release. 

 Because N. fucicola display no external sexual charac- 

 ters, sex of fish could only determined by the presence 

 of extruded gametes if fish were running ripe when cap- 

 tured, or by dissection at the conclusion of the study. 



At the conclusion of the tag-recapture study, each site 

 was fished intensively. Recaptured tagged fish were eu- 

 thanized by immersion in an ice-slurry. Fish captured 

 at Lord's Bluff were measured immediately after sacri- 

 fice; gonads were dissected to determine sex, and sagit- 

 tal otoliths were collected. Untagged fish were returned 

 immediately; therefore otoliths that were analyzed came 

 from tagged fish only. All fish captured at Point Bailey 

 were processed in a similar fashion but were stored 

 frozen prior to examination. 



Otolith preparation and interpretation 



Sagittal otoliths were mounted in a polyester resin block, 

 and transverse sections (250-300 ,um thick) were cut 

 through the primordium with a lapidary saw. Sections 

 were mounted on a slide and examined under a binocular 

 microscope at x25 magnification. The primary author 

 counted annuli and individuals were allocated to a year 

 class, and fractional ages were assigned based on an 

 arbitrary birthdate of 1 October, following the method 

 of Ewing et al. (2003). 



To determine if any significant differences existed 

 within or between reader estimates, a random sub- 

 sample of 55 otoliths, from both sites, was re-aged by 

 the primary reader (DW) and another experienced oto- 

 lith reader (GE). The frequency distribution of ages in 

 each population was then compared with a Kolmogo- 

 rov-Smirnov test. Consistency of age estimates was 

 also compared by using age bias plots (Campana, et 

 al., 1995) and the index of average percent error (IAPE 

 serisu Beamish and Fournier, 1981). 



Preliminary inspection of the length data for thawed 

 individuals from Point Bailey revealed many negative 

 growth increments when compared to length data col- 

 lected from recaptures prior to the conclusion of field 

 sampling. Repeated measurements of N. fucicola, con- 

 ducted independently of our study, have shown length 

 changes in the order of 8-9% in frozen and thawed 

 individuals compared to measurements from individu- 

 als alive or freshly euthanized (G. P. Ewing, unpubl. 

 data 3 ). Consequently, measurements taken from frozen 

 fish were deemed to be incompatible with measure- 

 ments taken from fresh fish and were removed from 

 the tagging and otolith data sets. Where data from 



Ewing, G. P. 2002. Unpubl. data. University of Tas- 

 mania, Tasmanian Aquaculture and Fisheries Institute, 

 Marine Research Laboratories. Nubeena Crescent, Taroona, 

 Tasmania 7053, Australia. 



