FISHERY BULLETIN: VOL. 87, NO. 1 



90 



70 



50 



30 



'Z 10 

 >, 50 



a 



30 



10 



30 



10 



21 °C 



" • group 1 



• • group 2 



I' • group 3 



•- • group 4 



« rf\—-- 



17 °C 



13°C 







2 4 6 8 



Days after First-Feeding Stage 



Figure 4.— Growth in dry weight of white perch larvae tested 

 under four food availabihty conditions and at three temperatures. 

 Plotted values are means ±2 SE. 



growth rates at all temperatures (Table 3). At 17° 

 and 21 °C group 2 larvae, delayed only 2 days, had 

 significantly reduced overall weight gains compared 

 to group 1 larvae (ANCOVA and SNK procedure, 

 P < 0.05). Weight gains after 8 days for groups 3 

 and 4 were significantly lower at all temperatures 

 (SNK procedure, P < 0.05) (Table 3). 



The mean instantaneous growth rates attained by 

 larvae at 2 d intervals showed several important pat- 

 terns (Fig. 5). At all temperatures, feeding at 800 

 versus 50 rotifer/L food levels produced significantly 

 different growth rates in 2 days or less (ANOVA, 

 P < 0.05). At 13°C, growth differences among food 

 groups were established after 2 days but became in- 

 consistent, while food group differences became 

 more pronounced at higher temperatures. At 17° 

 and 21 °C, larvae that had 2 d delays before being 



Table 3. — Regression equations describing growth in weight of 

 white perch larvae tested under four food availability conditions 

 and at three temperatures. Feeding duration was 8 days. In the 

 regression equation, W is dry weight in ng, t equals days after first- 

 feeding, G is the instantaneous growth coefficient, and W^ is dry 

 weight at time 0. Results of ANCOVA and multiple comparison pro- 

 cedures (SNK) also are given. 



T Food 

 (°C) group n 



Regression 

 equation 



SEr. 



Percent 



gain 

 (%cf-') 



ANCOVA result; The growth rates differ significantly (P < 0.001). 



SNK summary (different superscript numbers on each line indicate 

 significant differences among growth rates (P < 0.05)): 



Among food groups (FG): 



CO FG1 FG2 FG3 FG4 



offered the high food level (group 2) equalled group 

 1 growth rates after lag times of 2-4 days. Growth 

 recoveries from 4 d delays were slower and incom- 

 plete, but there were strong indications that group 

 3 larvae were initiating substantial growth during 

 the last 2 days of feeding. Group 4 larvae lost weight 

 from day 2 to day 4 and grew slowly throughout the 

 study. 



Instantaneous growth coefficient also was re- 

 gressed on temperature for each food group (Fig. 

 6). All four regression coefficients (slopes) differed 

 significantly among food groups (ANCOVA with 

 SNK procedure, P < 0.05). Growth rates of all food 

 groups diverged at a faster rate in the upper half 

 of the temperature range. Growth coefficients for 

 groups 1 and 2 larvae increased by factors of 

 3.5-4.0 within the temperature range tested (13°- 

 21°C). 



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