MARGULIES: EFFECTS OF FOOD AND TEMPERATURE ON WHITE PERCH 



(Fig. 3). At 17° and 21 °C, food level effects were 

 clearly demonstrated and the final lengths attained 

 by larvae in all food groups differed significantly 

 from each other (SNK procedure, P < 0.05). The 

 well-fed larvae in groups 1 and 2 were sigTiificantly 

 longer after 8 days of feeding at 17° and 21° than 

 they were at 13° (SNK procedure, P < 0.05). 



Depending on food and temperature conditions, 

 larvae grew in length at rates ranging from 0.01 to 

 0.28 mm/d (Table 2). The larvae in group 1 exhibited 

 the highest growth rate at all temperatures, grow- 



5.6 

 5.2 

 4.8 

 4.4 

 4.0 

 3.6 



T3 



3.2 

 5.2 



4.8 



4.4 



4.0 



3.6 



3.2 



4.0 

 3.6 

 3.2 



17 °C 



[• • group 1 

 ]• — -. group 2 

 •- -• group 3 

 • -group 4 



13 °C 



2 4 6 8 



Days after First-Feeding Stage 



Figure 3.— Growth in standard length of white perch larvae 

 tested under four food availability conditions and at three tem- 

 peratures. Plotted values are means ±2 SE. 



ing at 0.05 mm/d at 13°C, 0.20 mm/d at 17°C, and 

 0.28 mm/d at 21°C. At 17° and 2rC, larvae in 

 groups 1 and 2 grew significantly faster than those 

 in groups 3 or 4 (ANCOVA and SNK procedure, P 

 < 0.05). For either group 1 or 2, an increase in tem- 

 perature resulted in a significantly higher growth 

 rate compared to 13°C (SNK procedure, P < 0.05). 

 The linear regressions gave good fits to the growth- 

 in-length data, although there was some indication 

 that growth at 17° and 21 °C for groups 1 and 2 was 

 becoming more curvilinear after day 4 (Table 2, Fig. 

 3). 



Well-fed larvae (group 1) were significantly 

 heavier at all three temperatures (ANOVA and SNK 

 procedure, P < 0.05). At 17° and 2rC, final mean 

 weights of larvae from all food groups differed 

 significantly from each other (SNK procedure, P < 

 0.05). As temperature increased, weight increases 

 were most pronounced for groups 1 and 2 (Fig. 4). 



The well-fed group 1 larvae had the highest 



Table 2.— Regression equations describing growth In length of 

 white perch larvae tested under four food availability conditions 

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

 regression equation, L Is standard length In mm, / equals days after 

 first-feeding, b Is grovirth rate in mm. and a Is the y-lntercept. Results 

 of ANCOVA and multiple comparison procedures (SNK) also are 

 given. 



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): 



(°C) FG1 FG2 FG3 FG4 



67 



