30 



Fishery Bulletin 103(1) 



Panulirus marginatus 



10 20 30 40 50 60 70 80 90 



Tail width (mm) 



Figure 5 



Scatterplots of the relation between pleopod length and tail 

 width for the Hawaiian spiny lobster (Panulirus marginatus). 

 The morphometric maturation point (MMP: indicated by a 

 vertical line) represents the allometric threshold coincident 

 with sexual maturity ([Oo+fJ 12). 



as well as the duration of the intermolt. These specific 

 topics deserve future study. 



The above caveats notwithstanding, it is helpful to 

 compare estimates of body sizes at sexual maturity 

 based on various morphological and physiological evi- 

 dence and to ascertain the degree of agreement among 

 the estimates (Fernandez-Vergaz et al., 2000). The es- 

 timate of MMP (47.6 mm) indicated by the pleopod 

 length-to-TW relation for S. squammosus, for example, 

 was about 16% smaller than the median size at matu- 

 rity (55.5 [±1.35 SE] mm) estimated by using simple 

 presence-absence of berried eggs for the same series of 

 specimens. The latter estimate, however, is imprecise 

 and an overestimate. The long-term mean TW at 50% 

 maturity based on berried condition for the period from 

 1986 to 2001, indistinguishable among component years, 

 was 50.0 ±0.83 mm, more precise than the single-year 

 estimate although still biased high (DeMartini et al., 

 2002). If this 50.0 value is used for reference, the pleo- 

 pod length-based estimate of the MMP falls within <5% 

 of the long-term mean. For P. marginatus, the analogous 

 MMP = 36.4 mm value was within 3% of the estimated 

 median size at maturity (35.4 mm) based on the com- 

 bined criteria of berried eggs and sperm mass presence. 

 All the various estimates of functional maturity for the 

 two species were within 2.0-12.6% (mean=7.9%) of the 

 best respective estimate of gonadal maturity. These 

 close similarities, despite the inherent biases of the two 

 methods, indicate that maturity metrics such as relative 

 pleopod length can provide highly satisfactory proxies 

 of true functional maturity that are closely related to 

 gonadal maturity in certain cases. 



Pleopod length as a maturity metric 



In some Crustacea (once again, not lobsters, as far as 

 is known), allometries are not fixed at the pubertal 

 molt; and, in a minority of these, allometric growth 

 is seasonally cyclic and allometries disappear when 

 mature instars molt during nonreproductive periods 

 (Hartnoll, 1974. 1982). And body proportions may not be 

 strong predictors of sexual maturity for clawed lobsters 

 (Comeau and Savoie, 2002). In many, if not most, deca- 

 pods such as spiny lobsters (e.g., George and Morgan, 

 1979; Groeneveld and Melville-Smith, 1994), however, 

 relative appendage-to-body sizes, as well as obvious 

 morphological criteria such as the presence of berried 

 eggs and a sperm mass, indicate functional sexual matu- 

 rity. Body part allometries in some cases can be better 

 predictors of maturity than more obvious characters 

 like berried eggs. An incomplete measure such as per- 

 centage berried, exemplified by the slipper lobster (S. 

 squammosus) in the present study, can falsely fail to 

 detect reproductively inactive adult females. Appendage- 

 to-body size proportions thus have one major advantage 

 over other morphometries in that they permit reproduc- 

 tively inactive adult females to be correctly classified 

 as mature. This advantage is relatively unimportant 

 in other species like P. marginatus for which additional 

 gross morphological indicators such as the presence- 

 absence of a sperm mass complement the information 

 provided by berried condition. Even so, proportional 

 appendage lengths can be used in such cases as another 

 fairly inexpensive and independent measure that could 

 contribute to a multivariate assessment of maturity. 



