temperatures. The fish remained in the 

 experimental ponds for 10 days before ter- 

 mination of a test to observe any delayed 

 mortality. Mortality was recorded on the 

 day of occurrence. 



Controls conducted with the striped 

 bass experiments involved transfers in 

 which the change in salinity duplicated that 

 of the accompanying test, but with no 

 change in temperature. Shad controls in- 

 volved transfer of fish with no change in 

 temperature or salinity since preliminary 

 tests showed this fish could not tolerate 

 transfers from salt to fresh water without 

 mortality. 



Dissolved oxygen concentration was 

 determined in parts per million using the 

 Winkler method, and pH was determined 

 using a Hellige comparator. Salinity in 

 parts per thousand ("on) was determined 

 using a hydrometer (salimeter), and tem- 

 perature was recorded in degrees Fahren- 

 heit. 



Striped Bass Experiments 



Adult striped bass were tolerant to 

 transfers between salt and fresh water at 

 the different temperatures tested (table 1). 

 In the widest range temperature and sa- 

 linity change from salt to fresh water 



(salt water at 45 F. and 35 '^oo to fresh 



o 

 water at 74 F.), one early mortality oc- 

 curred (experiment 1). No deaths resulted 

 from salt to fresh water transfers over 

 lesser increments of either temperature 

 or salinity or both (experinnents 2 through 6). 



TABLE 1. — Abrupt transfers of adult striped bass between salt and fresh 

 water at different temperatures. 



In those tests involving change from water 

 at 45° F. to water between 74° and 80© f., 

 the fish turned ventral side up, apparently 

 as a result of shock, but usually they re- 

 vived in a few seconds. A single mortality 

 occurred in a transfer from fresh water 

 of 74° F. to salt water at 56° F. (experi- 

 ment 7), but no deaths occurred in other 

 fresh to salt water transfers at tempera- 

 ture differences as great as 31° F. (ex- 

 periments 8 through 10). No deaths oc- 

 curred among fish used as controls. 



American Shad Experiments 



Adult shad were tolerant to transfers 

 from fresh to salt water, but were much 

 less tolerant to transfers from salt to 

 fresh water at the different temperatures 

 tested (table 2). In the greatest tempera- 

 ture change (25° F.) employed intestsfrom 

 salt to fresh water, total mortality oc- 

 curred within Z\ hours (experiment 1). 

 These fish turned ventral side up imme- 

 diately after transfer, but quickly revived 

 and appeared normal until further distress 

 occurred 15 minutes later. Conflicting re- 

 sults occurred in other salt- to fresh-water 

 tests. In transfers over a 10° F. difference 

 in temperature, two nnortalities occurred 

 in experiment 2, and no mortality occurred 

 in experiment 3. In transfers with prac- 

 tically no change in temperature but with 

 salinity changes similar to those employed 

 in the above tests, greater mortality oc- 

 curred (experiments 4 and 5). Some shad 

 in each of the salt- to fresh-water tests 

 were observed to eject bubbles from their 

 mouths, at or near the surface of the 

 ■water. Fish in distress swam near the 

 surface apart from the school; no violent 

 movements accompanied death as the fish 

 simply sank to the bottom of the pond. 



TAfil.E 2. --Abrupt transfers of adult Aioerican shad between salt and 

 fresh water at different temperatures 



Seven fish used in this test. 



■'■ Nine fish used in this test. 



