YAMASHITA and BAILEY: BIOENERGETICS OF LARVAL WALLEYE POLLOCK 



Table 1. — Instantaneous rates of gastric evacuation and gut clearance time 

 related to age and feeding condition of larval walleye pollock at 6.4°C. Data were 

 fitted to the equation: A, = Ao e "' (see text). Also shown is the percent of 

 larvae in the experiments greater than 5.5 mm SL, as an indicator of those with 

 midgut coiling. 



Q) 10 



5 



o 

 O 



o 



15 



Time (h) 



Time (h) 



Figure 1. — Curves to describe food intake of low ration (A.) and high ration (B.) pollock larvae. Data were 

 fitted to the equation: S = Sn,ax ^ (1 - e"'' '), where S is percent dry weight of gut contents to larval 

 dry weight at time t (h) after initiation of light period; S^ax 's the as>Tnptotic gut content {%); and F is the 

 instantaneous rate of gut filling. Numbers after each line indicate age in days. 



constant (Table 2). About 10-12% seems to be 

 the maximum capacity of larval pollock guts 

 within the range of stages examined. These 

 measured maximum values are close to Smax 

 values predicted from the asymptotic gut con- 

 tent curve (Table 2). The value for 7 d old high 

 ration larvae was an exception; the ingestion 

 curve appeared to be nearly linear and the re- 

 sulting Smax high (Fig. 1; Table 2) 



To estimate daily ration, instantaneous rates 

 of gastric evacuation under specific age and feed- 

 ing conditions were taken from Table 1. At day 

 7, one day after feeding commenced, weight- 

 specific daily ration was low, about 24-29% 

 (Table 2). Daily ration increased to a level of 

 about 55% at days 13-16. In spite of the ob- 

 served constant values of maximum percent gut 



contents with age, daily ration decreased to 

 about 35% by day 21. The difference in daily 

 ration between the high and low ration condi- 

 tions was not significant (ANOVA, P > 0.1). 



Metabolic Rates 



Results of oxygen consumption rate measure- 

 ments are summarized in Table 3. From day to 

 day 4 after hatching there was no remarkable 

 difference in respiration between daytime {Mr^ 

 and night (Mre)- After day 6, when most larvae 

 commenced feeding, O2 consumption rate in- 

 creased as age and weight of larvae increased, 

 and Mro was from 25 to 68% higher than Mre- O2 

 consumption rates in the four conditions were 

 significantly different (ANOVA, P < 0.01). 



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