200 



160 



r^ 120 - 



GRUNION 



10 



8 



4 - 







HALIBUT 



Y=I4.5X +0.8 







.15 



.30 



.45 



.60 



.75 



6 8 10 



DRY WEIGHT ( mg • larva"') 



Figure 6. — Relation of lipofuscin fluorescence per larva to dry weight for larval grunion (upper left) white seabass (lower left), and 



California halibut (right). Note different axes. 



larvae to see if we could detect an increase in 

 lipofuscin. Table 3 shows results for seabass 

 starved for the final 20% of the rearing period; 

 there was no significant change in the concentra- 

 tion of lipofuscin. This is not what one would ex- 



pect if accumulation of lipofuscin is proportional 

 to physiological age, unless no lipid is metabo- 

 lized during starvation. However, this result also 

 could reflect slow transformation of lipofuscin 

 from a more to a less soluble pool (Vernet et al. 

 1988). 



Table 3. — Lipofuscin fluorescence (FU) per 

 unit dry weigfif of larval white seabass starved 

 for various periods after age 29 days. 

 N = number of analyses; ranges in parenthe- 

 ses. 



Conclusions 



Our intent was to evaluate the utility of mea- 

 suring extracted lipofuscin fluorometrically as an 

 indicator of the integrated metabolic health of 

 fish, especially preserved ones, and of relative net 

 efficiency of growth. We conclude that this tech- 

 nique is unlikely to be useful in these ways, at 

 least within the larval period. Although the accu- 

 mulation of total body burden of lipofuscin was 

 demonstrated, the variability among individuals 

 grown under the same conditions became so large 

 over time that we were unable to calibrate the 

 method in an ecologically meaningful sense. The 

 variability was evident in all measures of growth, 



413 



