Blood et al.: Embryonic development of Theragra chalcogramma 



21 1 



O 



/ 



J& * 



**.^*^w**** **•**.*** * ********* *.. ; 



3.8 C -+- 5.7 C * 7.7 C 



I 1 1 1 1 I : 1 1 1 1 1 1 1 1 1 1 



24 48 72 96 120 144 168 192 216 240 264 288 312 336 360 384 408 



Incubation time (h) 



Figure 1 



Temperatures recorded in water baths during incubation of Theragra chalcogramma eggs. 



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 CO 



c 

 CD 



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CD 



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24 48 72 96 120 144 168 192 216 240 264 288 312 336 360 384 408 



Incubation time (h) 



Figure 2 



Development of Theragra chalcogramma eggs incubated at 3.8°, 5.7°, and 7.7°C. Points represent occurrence of 

 stages at scheduled sampling times. 



The piece-wise regression model (SAS, 1985) has 

 two separate components and is discontinuous be- 

 tween stages 6 and 7 (Fig. 4). This type of model was 

 necessary because of the rapid divergence of devel- 

 opmental rates at all temperatures after stage 6; it 

 was not possible to fit one equation to the entire 

 incubation time. The two components are described 

 by the following equations: 



component 1: stages 1-6 



Age = 3.27 - 0.13 (stage) (temperature) 

 + 0.47 (stage 2 ); 



component 2: stages 7-21 



Age = 17.82 + 7.05(stage) - 0.656 (stage) 



(temperature) + 0.043(stage 3 ) - 0.0032 



(temperature) (stage 3 ), 



