DeMartini et al.: Validated morphological metric for lobster size at maturity 



27 



Table 1 



Results of tests of potential effects of various criterion variables on the accuracy (bias of delta-barsl and precision (CVs of deltas) 

 for measured lengths of first pleopod exopodites for slipper lobster (Scyllarides squammosus) and Hawaiian spiny lobster (Panu- 

 lirus marginatus) caught from Necker Bank, Hawaii. Delta-bar = mean paired-difference; samples sizes are n paired observa- 

 tions. 



Variable 



Slipper lobster 



Body side (left vs. right) 



Measurement aspect (ventral vs. dorsal) 



Measurement venue (shipboard vs. lab) 



Measurement venue (shipboard vs. lab) 



Measurer (A vs. B) 



Measurer (A vs. B) 



Spiny lobster 



Body side (left vs. right) 



Measurement aspect (ventral vs. dorsal) 



Measurement venue (shipboard vs. lab) 



Measurement venue (shipboard vs. lab) 



Measurer (A vs. B) 



Measurer (A vs. B) 



0.001 



1)1)01 



0.001 



0.001 



0.001 



0.22 



0.001 



0.001 



0.001 



0.001 



0.25 



0.31 



74 



63 



63 



63 



63 



63 



135 



33 



88 



Spiny lobster Year effects on pleopod-to-TW relations 

 for P. marginatus were likewise insignificant ( ANCOVA; 

 accept H : slopes equal, P>0.67; intercepts only 0.2% dif- 

 ferent) and data for both years were pooled for further 

 analyses. The MMP for the TW at which 50% of the P. 

 marginatus females exhibit a disproportionately long 

 pleopod was 36.4 mm (34.1-38.0 mm; Fig. 5). Figure 6 

 illustrates the corresponding estimate of median size 

 at functional maturity, 35.4 (33.7-37.1) mm TW, based 

 on the combined criteria of sperm mass and berried egg 

 presence, for P. marginatus. 



Estimated sizes at physiological maturity 



Gonadal maturity determined from microscopic staging 

 of histological ovary preparations indicated matura- 

 tion stages ranging from oogonial to fully vitellogenic 

 (Table 2; Minagawa and Sano, 1997) for the females of 

 each species. For both species, gonad indices (GIs) and 



median oocyte diameters generally increased over the 

 cycle of development even though berried specimens 

 exhibited lower GIs and oocyte sizes than unberried 

 adults of the respective species (Table 2). The ovaries 

 of mature females contained a preponderance of fully 

 yolked oocytes whose average minimum diameter (fol- 

 lowing dehydration and staining) was 0.24 mm and 

 0.30 mm for S. squammosus and P. marginatus, respec- 

 tively. The maximum observed diameter of fully yolked 

 oocytes was 0.60 mm (in S. squammosus) and 0.58 mm 

 {P. marginatus). 



The proportions of observed immature individuals 

 ranged from 32% to 38% of total female specimens 

 (depending on species) and were sufficient to construct 

 logistic curves relating percentage gonadal maturity to 

 body size for each species. Estimated median TWs at 

 gonadal maturity were 51.1 (48.6-53.5) mm and 40.5 

 (37.9-43.1) mm TW for S. squammosus (Fig. 4) and P. 

 marginatus (Fig. 6), respectively. 



