FISHERY BULLETIN: VOL. 74, NO. 1 



30 



26 



SALINITY %. 

 15 20 25 30 



35 



40 



45 



6 8 10 12 14 16 16 



TEMPERATURE "C 



Figure 3. — The mean hatching time of winter flounder 

 embryos for each temperature and sahnity. 



Effects of Temperature and Salinity 

 on Embryonic Development 



In each of the three experiments, general ob- 

 servations were made on the eggs, embryos, and 

 larvae (Figure 4). No development occurred in a 

 salinity of 0.5%; however, the eggs swelled ap- 

 proximately 20% before death occurred. A diame- 

 ter increase of 8 to 10% was also observed in eggs 

 held at 5%. Below 10°C, embryos held in 5% ap- 

 peared to develop normally, then died just prior to 

 hatching. At 10°C and above, most of the embryos 

 died during gastrulation. Embryos held in a sa- 

 linity of 10% had the highest mortalities just 

 prior to hatching and at hatching; many larvae 

 were observed dead partly emerged from the 

 chorion. Mortality occurred throughout develop- 

 ment at 12° and 14°C. 



In salinities between 15 and 30%, most mor- 

 talities occurred just prior to hatching, although 



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0.5 5 7.5 10 15 20 25 30 35 37.5 40 45 



SALINITY (%•) 



Figure 4.— The qualitative effects of temperature and salinity on the development and hatching of wdnter flounder embryos. 



56 



