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Fishery Bulletin 103(1) 



maturity). Confidence bounds on the MMP were estimat- 

 ed by using the studentized bootstrap method (Davison 

 and Hinkley, 1997) with 1000 iterations. 



In order to characterize median body size at gonadal 

 maturity, the percentage mature per 5-mm TW class, 

 deduced from viewing histological preparations of ova- 

 ries, was fitted to the conventional (2-parameter) logis- 

 tic model, 



P x = 100/{l + exp[-a(7W-6)]}, 



where P x = percent mature at TW = x; 



a and b are unknown constants; and 

 TW = tail width in mm. 



To similarly estimate median size at maturity based 

 on gross external characteristics, the percentage ma- 

 ture per 5-mm TW class was fitted to a 3-parameter 

 logistic model for Scyllarides squammosus and to the 

 conventional 2-parameter logistic for Panulirus mar- 

 ginatus. For S. squammosus, percentage maturity per 

 5-mm TW class was estimated by fitting the 3-param- 

 eter logistic equation, 



P v =100a/{l + exp[(46/o)(c-7TV)]}, 



where a = the asymptotic proportion berried; 



b = the slope of the logistic function at the inflec- 

 tion point; and 



c = TW SQ is the tail width at the inflection point 

 (size at 50% of asymptote). 



This function has been fully described for estimating per- 

 centage maturity based on incidence of ovigerous females 

 in iS. squammosus; the extra parameter is needed to fit 

 an asymptote to the sigmoidal function at a value less 

 than 100% (DeMartini et al., 2002). Parameters of the 

 various models were estimated by using the maximum- 

 likelihood nonlinear curve fitting procedure SAS NLIN; 

 all nonlinear regressions were weighted by the square 

 root of sample sizes. 



The body size at which 50% of the population was es- 

 timated as mature (hereafter referred to as TW 50 ) was 

 compared for 1) TW 50 based on the relative incidence of 

 berried individuals within the female population (both 

 species), adjusted for the co-presence of a sperm mass 

 (P. marginatus only), 2) TW 50 estimated from histologi- 

 cal evidence (both species), and 3) the MMP of the allo- 

 metric EL-to-TW relation (both species). Estimates were 

 compared graphically among methods for each species. 



Analyses of pleopod-based maturity followed a series 

 of evaluations of pleopod characteristics used to identify 

 a standardized metric. Measurement aspect (dorsal, 

 ventral) and side (right, left) were compared within 

 individuals by using paired £-tests. A randomized com- 

 plete block (RCB) ANOVA (SAS PROC ANOVA), with 

 specimen as the blocking factor, was used to evaluate 

 the effects of measurer and measurement venue (at 

 sea versus ashore) on the mean measurement bias and 

 precision (CVs) of pleopod measurements. 



Results 



Pleopod characteristics 



Measurement error, and effect of side of lobster and 

 aspect (ventral versus dorsal) on measurements Inher- 

 ent measurement error averaged 0.23 mm and 0.16 mm 

 (1.0% and 0.4%) for slipper and Hawaiian spiny lobster, 

 respectively, based on two independent measurements 

 by the same measurer. Exopodites of left-side pleopods 

 averaged 3% and 2% shorter than exopodites of right- 

 side pleopods for the two respective species (paired Mest; 

 both P<0.001; Table 1). Exopodites of first left pleopods 

 were 4% and 2% longer in ventral aspect for slipper and 

 spiny lobster, respectively, (RCB ANOVA; both P<0.001; 

 Table 1). 



Measurement venue A matched (same-specimen) series 

 of measurements made aboard ship versus in the labo- 

 ratory (all by the same measurer) indicated a system- 

 atic difference in left pleopod length ( ship > lab; RCB 

 ANOVA; both P=0.001) for slipper lobster and spiny 

 lobster (Table 1). For each species, however, the mean 

 difference between venues was trivial (0.2-0.4 mm or 

 0.6-1.4%). Differences between ship and laboratory were 

 detectable despite the consistently lower precision pro- 

 vided by shipboard measurements (shipboard CVs were 

 47% and 39% larger for slipper and spiny lobster, respec- 

 tively; RCB ANOVA: both P<0.001; Table 1). Absolute 

 differences between shipboard and lab CVs were small 

 for the respective species (0.2% and 0.7%; Table 1). 



Measurer effects An extensive series of shipboard inter- 

 measurer comparisons between pleopod length mea- 

 surements taken by one experienced (A) and a second 

 inexperienced (B) measurer indicated trivial systematic 

 differences between measurers (0.2%; RCB ANOVA; 

 P=0.25). Precision also was unaffected by measurer 

 (P=0.31; Table 1). 



Standardized metric It follows from the above that the 

 best measure available for use was the length (in ven- 

 tral aspect) of the left first exopodite. This metric was 

 used in all quantitative comparisons among maturity 

 assessment methods and is recommended for future 

 applications with these species. 



Estimated sizes at functional maturity 



Slipper lobster Pleopod-to-TW relations for S. squammo- 

 sus did not differ meaningfully between 2000 and 2001 

 (ANCOVA; accept H Q : slopes equal, P=0.11; intercepts 

 only 0.5% different) and both years' data were pooled for 

 further analyses. The estimated MMP (95% CI) for the 

 TW at which 50% of the female S. squami7iosus exhibit a 

 disproportionately long first left exopodite was 47.6 mm 

 (45.1-49.4 mm; Fig. 3). Estimated median body size at 

 functional maturity based on presence or absence of ber- 

 ried eggs, using the same series of 2000-01 specimens, 

 was 55.5 (52.7-58.3) mm TW (Fig. 4). 



