BAILEY: EARLY LIFE HISTORY OF PACIFIC HAKE 



RESULTS 



Development Times 



Egg hatching time shows a marked response 

 to temperature (Fig. 1 ). Time for 50% hatching of 

 eggs collected at Port Susan ranges from 3.5 d at 

 15°C to 4.5 d at 12°C (coastal temperature range 

 at 50 m depth is 11°-14°C) and 6.5 d at8°C (the 

 approximate temperature at Port Susan). Also 

 shown in Figure 1 are the mean hatching times 

 of eggs collected off California that were report- 

 ed by Zweifel and Lasker (1976). 



The time from hatching to complete absorp- 

 tion of the yolk sac is also temperature dependent 

 (Fig. 2). The time for 50% of the sample larvae to 

 completely utilize their yolks is 9.7 d at 10°C, 6.4 

 d at 12°C, and 4.2 d at 15°C. I was notable to rear 



160.0 



60.0 



8-0 



9.0 



10-0 



11.0 12-0 



TEnPERATURElt) 



13-0 



14.0 15-0 



Figure 1.— Effect of temperature on time to 50% eggs hatch- 

 ing for Pacific hake, and 95% confidence intervals. Small 

 solid circles are hatching times from Zweifel and Lasker ( 1976). 

 Data was fitted to a Gompertz curve: Y = 484.00 * exp(-2.89 

 * (1 - exp( -0.0623 * X))). 



8.0 



9.0 



10.0 



11.0 12.0 



TEttPERflTURE(t) 



13.0 



14.0 



15-0 



FIGURE 2.— Effects of temperature on 50% time to complete 

 yolk-sac absorption for Pacific hake larvae and 95% confidence 

 intervals. Data was fitted to a Gompertz curve: Y= 1,269.52 

 * exp(-108.82 * (1 - exp( -0.0016 * X))). 



larvae to yolk-sac absorption at 8°C. At 8°C, 8-12 

 d old larvae still had considerable yolk supplies 

 and no functional mouth. A well-developed 

 mouth normally formed after 4 d at 12°C and 

 after 3 d at 15°C. 



Both the mean and the maximum length of 

 time to starvation after complete utilization of 

 the yolk decreased with increasing temperature 

 (Table 1). A nonparametric analysis of variance 

 (Kruskal-Wallis; Conover 1971) indicates that 

 temperature has a significant effect on the time 

 to starvation (P<0.01). The variance in the mean 

 time to death was large in these experiments due 

 to death occurring not only from starvation, but 

 from other causes such as being trapped in the 

 surface film. These early nonstarvation deaths 

 were excluded from the analysis. 



Table 1.— Starvation experiments. 



Tempera- 

 ture (°C) 



Mean time to 

 starvation (h) 



Standard 

 deviation 



1 00% starva- 

 tion (h) 



No. of 

 larvae 



8 

 12 

 15 



251 

 200.2 

 150.0 



656 

 29.1 

 178 



318 

 235 

 168 



Growth Rates 



Larvae were reared in the laboratory beyond 

 the yolk-sac stage (±1 d) to verify otolith incre- 

 ments as daily marks. Increments begin to be 

 added 1-2 d before complete yolk-sac absorption, 

 perhaps coinciding with the onset of feeding; 

 after yolk absorption, 1 ring is apparently added 

 each day (Fig. 3). Rings on these otoliths were 

 much fainter than those of field-caught speci- 

 mens, possibly due to poor feeding, lighting, or 

 other rearing conditions in the lab. Postyolk-sac 

 larvae grown in the laboratory survived up to 10 



n 



10 

 9 

 8 



CD 7|- 



t— 



z _ 



LU 6 



o= 5 

 <_) 

 z 

 - 4 



3 



2 



1 

 



5 6 

 HCE OflYS 



10 11 



Figure 3.— The daily addition of increments by laboratory- 

 reared postyolk-sac Pacific hake larvae. 



591 



