nauplii/hr /larva at 23*^C to 17.6 nauplii/hr /larva at 29°C. These rates increased 

 exponentially as larvae grew, so that larvae were consuming 53.8 

 nauplii/hr/larva at 23°C and 142.7 naupHi/hr/larva at 29*^C at 16 days of age. 

 Rations, in terms of numbers of nauplii and dry weight consumption, were 

 then calculated. Specific ration also was calculated, and it tended to decrease as 

 larvae grew, particularly at the highest temperature (29°C), where it was 220.8 

 percent at two days after hatching but decreased to 79.7 percent at 8 days. 

 This result is similar to that of Laurence (60) for winter flounder (8°C), where 

 specific ration decreased from over 300 percent for the smallest larvae to about 

 30 percent for metamorphosed individuals. Mean gross growth efficiency of sea 

 bream (92) varied from 23.9 to 30.6 percent, the highest value being obtained 

 to the lowest temperature (23°C); there was no evidence that growth 

 efficiency changed with age. Mean growth efficiencies were similar to those for 

 winter flounder (60), except that first feeding winter flounder had low growth 

 efficiencies, which increased rapidly during the first few days of active feeding. 

 The relatively high growth efficiency of sea bream, when it begins to feed, 

 suggests that food is less critical for it than for winter flounder at that stage, a 

 suggestion supported by the relatively low required prey concentration for 

 survival of sea bream larvae (45). 



Starvation Criteria 



Because starvation is suspected as a major cause of larval mortaUty, 

 biochemical, histological, and behavioral criteria have been developed for some 

 species to show changes that occur when the food supply is inadequate. These 

 techniques eventually may be used to characterize starving larvae collected at 

 sea. Biochemical methods also have been used to show how laboratory-reared 

 larvae differ from wild larvae. When supported by morphometric data, 

 biochemical criteria hold promise to evaluate how types and amounts of food 

 affect larval condition. 



The biochemical composition of laboratory -reared, larval Atlantic herring 

 and plaice was studied by EhrUch (32, 33). He found that water, triglyceride, 

 carbohydrate, nitrogen, carbon and ash content varied as a percentage of body 

 weight as larvae grew, In starving larvae both relative (percentage) and absolute 

 changes in amounts of those substances were measured, the relative changes 

 often being a better measure of starvation than the absolute changes. 

 Percentage of water increased about four percent in starved larvae of both 

 herring and plaice, while percentages of triglyceride, carbohydrate, and carbon 

 decreased. Percent nitrogen decreased in starved plaice larvae but did not 

 decrease in herring; absolute amounts of nitrogen decreased in both species. 

 Ash percentage of both species increased rapidly during starvation. Ehrlich (32, 

 33) concluded that the "point of no return" was not defined by an abrupt 

 change in the chemical composition at some point during starvation, but rather 



185 



