and salinity. It has been established that 

 the young of certain anadromous fishes 

 cannot tolerate high salinity until they 

 approach the normal time of migration 

 to the sea (Rounsefell and Everhart, 1953). 

 Houston (1957) found that in juvenile salnnon, 

 marked positive reactions to concentrated 

 sea water occurred only in that stage of 

 development when the fish would normally 

 migrate seaward. Juvenile shad used in 

 the present experiments may not have 

 been physiologically adjusted for migra- 

 tion to the ocean. 



The greatest mortality of adult fish 

 usually occurred during the second to the 

 fifth day after transfer, while the greatest 

 mortality of juveniles occurred within 24 

 hours after transfer. The longer period 

 of survival of adults compared to that of 

 juveniles may have been due in part to 

 their larger size. Huntsman and Hoar 

 (1939) found that, in young salmon, the 

 larger the fish the longer it survived 

 high salinity. The authors concluded that 

 with increase in size young salmon became 

 more resistant to sea water to the degree 

 to which the exposed surfaces, through which 

 the sea water must act, became less in 

 proportion to the mass of the body, in 

 particular, the blood. 



When acclimating adult striped bass and 

 shad to a water temperature of 74° F. and 

 juvenile shad to a water temperature of 45° 

 F. (temperatures desired for initial en- 

 vironments), distress and mortality oc- 

 curred among the fish. Doudoroff (1942) 

 discussed the limiting effects of heating 

 and cooling upon fish and concluded that 

 acclinnation to cold was relatively slow. 

 In addition, seasonal variations in lethal 

 temperatures have been found for various 

 fish corresponding to the temperature vari- 

 ation of their normal habitat (Brett, 1944). It 

 follows that in the present tests either 

 acclimation was too rapid or possibly the 

 temperatures were in themselves adverse 

 to the fish. Experimental facilities and 

 seasonal availability of fish necessitated 

 conducting tests involving acclimation to 

 74° F. at a time when normal water tem- 

 perature was approximately 55° F., and 

 acclimation to 45° F. was attempted when 

 normal water temperature was approxi- 

 mately 70° F. In each case when the fish 

 were returned to water of normal tem- 

 perature, they immediately resumed natural 

 activity. 



SUMMARY AND CONCLUSIONS 



1. Experiments were conducted to de- 

 termine what effective abrupt transfers 

 between salt and fresh water, of different 

 temperatures, would have on adult and 

 juvenile striped bass and American shad. 

 Transfers were made at specific tempera- 

 tures and salinities over ranges from 45° 

 to 80° F. and to 35 °oo. Experiments 

 were also conducted to determine the ability 

 of juvenile striped bass and shad to ac- 

 climate to gradual changes in temperature 

 and salinity over ranges not tolerated with 

 abrupt transfer. 



2. Adult striped bass were tolerant 

 to abrupt changes between salt and fresh 

 water at differences in temperature over 

 the range 45° to 80° F. 



3. Juvenile striped bass survived 

 abrupt transfers between salt and fresh 

 water at differences in temperature over 

 the range 55° to 70° F., but were not tol- 

 erant to transfers from fresh water at 

 these temperatures to salt water of 45° F. 



4. Adult shad survived abrupt changes 

 from fresh to salt water at the same tem- 

 perature and at a 16° F. difference in 

 temperature. They displayed some tol- 

 erance to abrupt transfers from salt to 

 fresh water at the same temperature and 

 at a 10° F. difference in temperature, but 

 showed no tolerance at a 25° F. tempera- 

 ture change. 



5. Juvenile shad survived abrupt 

 transfers from salt to fresh water at 

 temperature differences over the range 45° 

 to 70° F. They were not tolerant to abrupt 

 changes from fresh to salt water at tem- 

 perature differences over the range 70° to 

 45° F. 



6. In transfers conducted within fresh 

 water, juvenile striped bass mortalities 

 occurred only in changes from water of 

 70° or 55° F. to water of 45° F. Juvenile 

 shad mortalities occurred in all tests 

 where temperature decrease was 7° F. or 

 greater. For both species, however, mor- 

 tality was less in tests conducted within 

 fresh water than in tests conducted from 

 fresh to salt water over identical tem- 

 perature differences. No mortality of ju- 

 veniles of either species resulted from 

 fresh water transfers at an increase in 

 temperature over the range 45° to VU^ j;'. 



