mortality resulted, however, in transfers 

 from fresh water at 70 or 55 F. to salt 

 water (33 °oo) at 45 F., and low mortality 

 occurred in transfers from these same ini- 

 tial conditions to fresh water at 45 F. 



Test fish momentarily turned ventral side 



o o 



up after transfers from 70 to 45 F. water, 



but this did not necessarily indicate later 



distress or mortality. No juvenile striped 



bass deaths or distress occurred in abrupt 



changes from salt to fresh water over the 



tennperature range 45 to 70 F. or in 



transfers within fresh water at increases 



in temperature over the same range (table 4). 



TABLE 3. — Abrupt transfers of Juvenile striped bass from fresh 

 water to fresh or salt water at different temperatures 



[Ten fish in each test] 



TABLE A. — Abrupt transfers of juvenile striped bass frcan fresh 

 or salt water to fresh water at different temperatures 

 [Ten fish in each test] 



All control fish survived with the exception 

 of single nnortalities in each of three con- 

 trols . 



Juvenile striped bass were able to 

 acclimate to gradual change in tempera- 

 ture, but not to change in both temperature 

 and salinity over the range in which mor- 

 tality occurred in abrupt transfer. In two 

 identical experiments, no distress took 

 place within 48 hours after a 3-hour tem- 

 perature decrease from 70° to 45° F. How- 

 ever, in a test employing a decrease in 

 temperature from 70° to 45° F. with step 

 increases in salinity from to 33 oo (0 °or 

 at 70° F.; 10 °oo at 62° F.; 20 °bo at 55° F.; 

 and 33 °bo at 45° F.) over 3 hours, a 50 

 percent mortality resulted within 48 hours. 

 These conditions were repeated over a 

 6-hour period, and 50 percent mortality 

 again occurred within 48 hours. 



American Shad Experiments 



Juvenile shad were not tolerant to 

 transfers from fresh to salt water at the 

 different temperatures tested, nor to tem- 

 perature decreases within fresh water. 

 They were tolerant, however, to transfers 

 from salt to fresh water and to temperature 

 increases within fresh water. All fish 

 succumbed to changes fronn fresh water 

 of 70° F. to salt water (33 "oo) of 45° or 

 55 °F. (table 5). Total or appreciable mor- 

 tality occurred in all other tests from 

 fresh to salt water over lesser tempera- 

 ture differences. Total mortality likewise 

 resulted from transfers conducted within 

 fresh water from 70° F. to 45° or 55° F. 

 At lesser temperature differences, fewer 

 mortalities generally occurred in fresh 

 water transfers than occurred when salinity 

 was also involved. No juvenile shad deaths 

 or distress occurred in changes from salt 

 to fresh water over the temperature range 

 45° to 70° F. or in transfers within fresh 

 water at increases in temperature over the 

 same range (table 6). Other than single 

 mortalities in each of three controls, all 

 control fish survived. 



Juvenile shad were able to acclimate 

 under certain conditions to a gradual de- 

 crease in temperature or increase in sa- 

 linity (table 7). They successfully ac- 

 climated to a 6-hour temperature decrease 

 from 70° to 55° F., but did not adjust to 

 a 15-hour decrease from 70° to 45° F. The 

 majority of test fish died after a 1.5-hour 

 increase in salinity from to 32 oo at the 



