FISHERY BULLETIN: VOL. 73, NO. 2 



20 



25 30 35 



SALINITY (7oo) 



40 



45 



Figure 5. -Twenty- four hour upper median thermal tolerance 

 limits (TLm) at various salinities for larvae acclimated to 21°, 

 24°, 27°, and 30°C. 



between 29° and 31°C, depending on the acclima- 

 tion temperature. Larvae could resist higher 

 temperatures for shorter periods of time. 



Salinity Tolerance 



The 24 h upper TLm for salinity v^^as not greatly 

 affected by the acclimation salinity and ranged 

 from 43 to iS.b^/oo, but the 24-h lower TLm was 

 appreciably higher among larvae incubated at 

 higher salinities (Figure 6). The lower TLm's (24 h) 



15 20 25 30 35 40 



ACCLIMATION SALINITY (%o) 



Figure 7.-Upper and lower median tolerance limits (TLm) of 

 salinity for a 48-h exposure. 



for larvae acclimated to 15 and 20^/oo were 4.2 and 

 S.5^/oo, respectively, whereas those for larvae 

 acclimated to 30 and 35°/oo were 10 and le.S^/oo, 

 respectively. The major difference between the 

 24-h TLm's and those for 48 and 72 h is the 

 progressive lowering of the upper TLm for larvae 

 acclimated to low salinities (Figures 7, 8). The 

 upper TLm for larvae from 15"/ oo shifted from 

 46.2V 00 at 24 h, to 36.6Voo at 48 h, and to 30.0V oo at 

 72 h; between 24 and 72 h, the upper TLm re- 

 mained the same (43Voo) for larvae acclimated to 

 40V 00, and decreased only from 48 to 46.2"/ oo for 



15 20 25 30 35 40 



ACCLIMATION SALINITY (%o) 



Figure 6.-Upper and lower median tolerance limits (TLm) of 

 salinity for a 24-h exposure. Larvae were acclimated to various 

 salinities at 24°C. 



5 2 25 



ACCLIMATION 



30 35 



SALINITY (%o) 



Figure 8.-Upper and lower median tolerance limits (TLm) of 

 salinity for a 72-h exposure. 



252 



