The best conditions for hatching and 24-h larval 

 survival were 30Z. salinity and 25° C (Table 1). 

 Analysis of variance of the hatching data showed 

 temperature (T) and the temperature-salinity 

 interaction iTxS) effects to be of borderline sig- 

 nificance (0.10>P>0.05); only salinity was sig- 

 nificant (P<0.05) (Table 2). A pattern of decrease 

 in percent hatch with increase in temperature at 

 the lower salinities (15 and 201), but not at the 

 higher salinities (Table 1), is indicative of the 

 TxS interaction. Hatching was significantly 

 greater at the two higher salinities than at lower 

 salinities (Table 3). 



Survival of larval red drum to 24 h was influ- 

 enced by both temperature and salinity. Poorest 

 survival was at 30° C and 151, (Table 3). 



Temperature was associated with significant 

 differences in survival of 2-wk-old larvae (Table 

 2). The lowest temperature (20° C) resulted in 

 reduced survival rate. The effect of temperature 

 on larval growth rate was pronounced; growth at 

 20° C was much slower than at 25° or 30° C (Table 

 4). Salinity had little influence on grovd;h. 



Discussion 



Salinity was important for hatching and 24-h 

 survival but not for 2-wk survival. Red drum eggs 

 developed successfully to feeding larvae at salin- 

 ities of 10-401, at 25° C; at other temperatures 

 the salinity range for 75% hatch was reduced to 

 15-30Z.. In low salinities, eggs sank to the bottom; 

 as Fonds (1979) explained for the common sole, 

 Solea solea, crowding and possible respiratory 

 stress contributed to reduced survival under these 

 conditions. In natural populations high mortal- 

 ity of eggs developing on the bottom would be 

 expected. 



Red drum eggs may have been acclimated to the 

 higher salinities since salinities for best hatching 

 were very near the salinities of the maturation 

 and spawning tanks (26-307J. Solemdal (1967) 

 reported that the osmotic concentration of the 

 ovarian fluid affected the buoyancy of flounder 



Table 3. — Mean percentage hatch, 24-h survival, and 2-wk 

 survival of red drum over all conditions. Individual means were 

 compared using Duncan's multiple range test. Any two means 

 connected by the same line were not significantly different 

 (P<0.05). 



Item 



15/., 207. 25/. 30/ 



20" C 25° C 30° C 



% hatch 



% 24-h survival 



% 2-wk survival 



76.46 86.54 96.17 98.42 96.09 86.47 87.87 



64.57 75.19 81.79 84.20 

 6.00 4.17 5.42 4.92 



98.04 94.71 75.42 

 0.37 8.00 7.00 



Table 4. — Standard length (millimeters) of red drum larvae 

 that survived 2 wk. 



eggs and that both could be changed experimen- 

 tally. Kinne and Kinne (1962) found that the 

 salinity of the water in which the parents lived 

 affected the response of developing cyprinodont 

 fish to salinity. Differences in response were 

 explained as being primarily nongenetic adapta- 

 tions to the spawning salinity (Kinne 1962). 

 Conversely, May (1975) found salinity tolerance of 

 Bairdiella icistia eggs was not affected by accli- 

 mation of the parent fish to low salinity and 

 suggested that salinity responses determined for 

 eggs accurately predict reaction to different salin- 

 ities in nature. 



Temperature became increasingly important as 

 the larvae developed. Apparently contradictory 

 results showed low temperature (20° C) to be 

 superior for 24-h survival, but inferior for 

 2-wk survival and growi;h. With low temperature, 

 development and probably metabolism were 

 slowed to the extent that grow^th and even mortal- 

 ity were delayed. The time spent in the yolk-sac 

 stage is temperature dependent; ranging from 40 

 h at 30° C to 85 h at 20° C (Holt et al. 1981). 

 Blaxter (1969) cautioned that high yolk-sac utili- 

 zation efficiency may result from low activity 

 which becomes a liability when it is reflected in 



Table 2. — Analysis of variance of percent hatch and survival of red drum eggs and larvae 

 subjected to various temperature-salinity conditions. 



Source 



% hatch 



24-h-old larvae 



2-wk-old larvae 



df 



MS 



df 



MS 



df 



MS 



Temperature (T) 2 459.94 2.44 0.09 2 3.090.70 16.43 0.00 2 450.69 20.66 0.00 



Salinity (S) 3 1.634.80 8.67 3 1.386.77 7.37 3 4.56 .21 .89 



TxS 6 400,18 2.12 .06 6 352.40 1.87 .10 6 6.54 .30 .92 



Error 84 188.41 60 188.12 12 21.82 



571 



