ROGERS: EFFECTS OF TEMPERATURE AND SALINITY ON WINTER FLOUNDER 



Table 4. — Analysis of variance for the effects of tempera- 

 ture and salinity on the survival and hatching of winter 

 flounder embryos. 



Source of 

 variation 



Total 



Salinity 



Temperature 



Residual 



"significant at P = 0.005. 



Table 5. — Duncan's multiple comparison of means for 

 temperature-salinity studies of winter flounder embryos. 

 (Means with similar symbols denote similar mean survi- 

 val percentages.)' 



Salinities 



Mean survival 

 (%) 



0.5 

 5.0 

 7.5 

 10.0 

 15.0 

 20.0 

 25.0 

 30.0 

 35.0 

 37.5 

 40.0 

 45.0 



0.0 V 

 1 . 1 v 

 21.6" 

 53.7° 

 69.9t 

 74.3t 

 67.4t 

 52.6° 

 35.6^ 

 40.3x 

 15.3* 

 0.0 V 



'P = 0.05. 



salinities and allows a grouping of each in order 

 of its significance (Table 5). The grouping of the 

 hatch means for variations in both temperature 

 and salinity coincides closely with viable hatch 

 curves illustrated in Figure 1. 



Incubation Time and Duration of 

 Hatching Interval 



The time to 50% hatch and the total range of 

 hatching time for each temperature and salinity 

 combination are recorded in Table 6. Figure 2 il- 

 lustrates the time to 50% hatch and the mean 

 incubation time for each temperature and salin- 

 ity respectively. The mean hatching interval 



26 



> 22 



< 



o 18 



< 



X 



14 



10 



2 - 



5. 00 



4.0 C 



% 



10 



15 



20 25 30 



SALINITY (%.) 



35 



40 



FIGURE 2. 



-The effects of salinity on the time to 50% hatch of 

 winter flounder embryos. 



ranges from 25 days at 3°C (10%) to 7 days at 12° 

 and 14°C (37.5 and 35% respectively). Individual 

 eggs hatched in as few as 5 days in most salinities 

 at 12° and 14°C, but took as long as 31 days at 

 3°C (10%). An inverse relationship for tempera- 

 ture with respect to the duration of hatching time 

 is evident. 



There is also a trend toward the same inverse 

 relationship with respect to salinity as can be 

 seen in Figure 2 where the time to mean 50% 

 hatch at all temperatures decreased slightly with 

 increasing salinities. This phenomenon of greater 

 hatching time at low salinities was noted in 

 Pacific cod eggs by Forrester and Alderdice 

 (1966). When salinity means versus incubation 

 time is considered by least squares regression, 

 there is a low correlation coefficient and a regres- 

 sion relationship is not applicable (Figure 3). 

 However, temperature means have a high corre- 

 lation coefficient and there is a strong regression 

 relationship present. 



Table 6. — Time in days to 50% hatch. Range of hatching interval in days shown in 

 parentheses. NH denotes no hatch. 



55 



