316 



Fishery Bulletin 102(2) 



2000 



1500 



1000 



500 



L= 129mm Er 



- C= 0.323 mg/mm 2 



30283e<' 1 24D-6.19C-0.024L+0.059f.C) 



Maximum Observed D 



(0.771) b 



i 



I 



.Yolking 



Begin 

 Ovulation 



t — i — i — i — i — i — rn — I — I — I — I — I I I I I I I I 



0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 

 Maior axis of smallest oocyte (D) (mm) 



2000 - 



1500 



1000 - 



500 - 



L = 129mm 

 D= 0.771mm 



Minimum Observed C 

 (0.323) 



0.2 



0.3 



0.4 



T 



— I — 

 0.8 



0.5 0.6 0.7 0.8 

 Mantle condition index (C) (mg/mm : 



"l 1 



1.0 



Figure 8 



Changes in the standing stock of oocytes predicted by Equation 

 16 (equation also given at top of panel) when major axis of small- 

 est oocyte (D) is varied and mantle condition index (Cl held con- 

 stant (upper panel), and when C is varied and D held constant 

 llower panel). The major axis size of oocyte when yoking begins 

 and when ovulation begins is also indicated, as are the maximum 

 observed D and minimum observed C. Substitution of the latter 

 two values into the equation yields the standing stock of oocytes of 

 females close to the end of their reproductive activity and is consid- 

 ered to be a minimum estimate of residual fecundity. 



line that expresses oocyte standing stock for the average 

 mature female of 130 mm as a function of mantle condi- 

 tion. In addition to the hypothetical line, we plotted the 

 total standing stock of oocyte and ova (E YD ) and mantle 

 condition index for all 147 mature females used for direct 

 fecundity determinations (Fig. 9). Our hypothetical line, 

 based on direct proportionality between egg dry weight 

 and body dry weight, follows the general trend in the 

 data, indicating that energy reserves in mantle tissue 

 may largely support the production and spawning of 

 eggs. Of course, actual energy costs would be higher 

 because metabolism, other somatic tissue, and conversion 

 efficiency of mantle tissue to eggs are not considered. The 

 lowest observed C in the fecundity data set was 0.323 and 

 the lowest C observed in the 1275 mature females from 

 the landed catch was 0.263. Using the above preovulatory 

 C (0.798 mg/mm 2 ), we determined that these values of C 



are equivalent to 60% and 67% losses in body dry weight 

 for these individuals. Fields (1965) suggested body wet 

 weight declined by as much as 50% , which is consistent 

 with our results. 



These rough calculations support the long held belief 

 that oocyte maturation is supported primarily by body 

 reserves. Some feeding occurs during spawning; L. opal- 

 escens has been observed feeding under lights at night 

 on the spawning grounds (Butler 2 ). Maxwell and Hanlon 

 (2000) observed L. pealeii feeding between egg-laying 

 bouts when they were held in the laboratory. Feeding be- 

 tween spawning bouts by the more robust spawners that 

 may migrate on and off the grounds each day seems quite 



2 Butler, J. 2000. Personal commun. Southwest Fisheries 

 Science Center. National Marine Fisheries Service, 8604 La 

 Jolla Shores Dr., La Jolla, CA 92037. 



