Ju et al: Demographic assessment of Callinectes sapidus 



317 



2.5  



2 - 



1.5 



1  



0.5 - 



4th mode (99/00) 

 3rcl mode (98/99) 



2nd modes 



3rd mode (99/00) 



1 St modes 



-+- 



0.25 0.5 0.75 



LF index (ug-LF/mg-protein) 



1.25 



Figure 4 



Mean (circle and square) ± standard deviation (error bar) of each mode estimated from modal 

 analyses of the lipofuscin index ( see Table 3 ). Circles and squares represent 1998-99 and 1999-2000 

 winters, respectively. Age was calibrated by using the empirical lipofuscin index accumulation rate 

 (Age (yr)=0.824 x exp" "^ "^''"■'^"') from Ju et al. (2001) and shown as a dotted line. 



lipofuscin-based ages. In past studies on crustaceans (e.g. 

 O'Donovan and Tully, 1996), lipofuscin has been shown to 

 be significantly influenced by metabolism, leading some 

 authors to conclude that lipofuscin is a closer measure of 

 physiological than chronological age. Recent work on labo- 

 ratory- and pond-reared crabs, however, has shown that 

 LF accumulation is relatively constant and that average 

 winter and summer rates differ by 21'7( (Ju et al., 2001). 

 During winter months LF continued to accumulate in the 

 eyestalks of pond-reared crabs, even though growth in CW 

 ceased on account of winter temperatures. Further, the 



lipofuscin-index versus age relationship in these rearing 

 studies (coefficient of determination: r2=78'Xf ) was substan- 

 tially less variable than the CW versus age relationship 

 (r2=59%). Nevertheless, variance in the lipofuscin index 

 versus age relationship is sufficient to cause misclassi- 

 fication of individuals, and it is important to obtain suf- 

 ficient samples to permit age modes among cohorts to be 

 resolved. 



The protracted spawning season for Chesapeake Bay 

 blue crabs (mid-May through mid-September; Van Engel, 

 1999) has important implications for subsequent size and 



