o 



>- ~ 



2 



2 



HI 



< 



CO 



3 



o 



UJ 



z 

 < 



z 

 o 



I- 

 < 



N 



< H 



I- z> 



CO 



z 



3.00 



2.50 



2.00 



1.50 



1.00- 



C 0.50 - 



0.00- 



Gulf Menhaden 

 Y= 0.736+0. 12426(X) 

 r a = 0.95 



_L 



14 16 18 20 22 24 



TEMPERATURE °C 



Figure 2.— The effects of temperature on the instantaneous 

 rate of yolk utilization for gulf menhaden. 



dicating a similar response to temperature by both 

 species. But the Y-intercepts differed significantly 

 (P = 0.02) indicating that, over the range of tem- 

 peratures tested, the Atlantic menhaden fed at a 

 significantly earlier age than gulf menhaden. For 

 both species the age at first feeding declined ex- 

 ponentially with increasing temperatures. Atlantic 

 menhaden were larger than the gulf menhaden at 

 first feeding (Fig. 3). At 20° C, Atlantic and gulf 

 menhaden growth rates were similar (ANCOVA, P 

 = 0.36), but Atlantic menhaden maintained a size 

 advantage during the early larval period (Table 2). 

 This difference was attributed to differential size 

 and age at first feeding. 



The ability of early larvae to withstand the depri- 

 vation of food was influenced by temperature (Table 

 3). Although at 20 °C mortalities may be attributed 

 to causes other than starvation (compare control and 

 starved), at progressively higher temperatures lar- 

 vae are less able to withstand the deprivation of 

 food. For example, at 24°C, gulf menhaden must 

 find food within three days after the onset of first 



5.5- 



5.0- 



4.5- 



4.0 

 8 



6 



4 



2 



• Atlantic Menhaden 

 o Gulf Menhaden 



/ 

 Y=30.7e-°- 11454 

 r 2 =0.99 

 _l L 



Y=25.1e 

 / r 2 = 0.96 



-0.0929(X) 



14 16 



18 



20 22 



24 



TEMPERATURE °C 



Figure 3.— The size and age when gulf and Atlantic menhadens begin feeding on exogenous food sources 

 at different temperatures. Each point represents a sample of about 10 fish. Replicate experiments were 

 only conducted for gulf menhaden and only at 14°, 20°, 22°, and 24°C. 



993 



