LEGGETT and WHITNEY: WATER TEMPERATI.IRE AND SHAD MIGRATIONS 



tion. In particular years the ocean temperature 

 regime may vary and change the usual locations 

 of the shad. Moreover, we have related shad 

 migrations to surface temperatures only. There 

 is at present no information on the depths at 

 which shad migrate. Walburg and Nichols 

 (1967) recorded shad that were trawled at 

 depths of 87 to 126 fm, and Leggett has similar 

 records of recoveries of tagged shad at depths 

 of 20 to 70 fm, again by trawl. These records 

 do no more than provide estimates of the max- 

 imum depths at which shad migrate. These fish 

 may have been captured near the surface as the 

 trawl was being recovered. 



On the basis of our observations on the be- 

 havior of shad in relation to temperature, we 

 believe that the effect of a significant elevation 

 of the temperature of a northern stream might 

 be to initiate the shad run at an earlier date, 

 provided that ocean temperatures are within the 

 proper range. In a southern stream like the St. 

 Johns River, Fla., where the run occurs during 

 the natural cooling phase rather than the warm- 

 ing phase of the river, elevated temperatures 

 could destroy the run of shad. 



ACKNOWLEDGMENTS 



We are grateful to Daniel Merriman and Lyle 

 M. Thorpe, Directors of the Connecticut River 

 Ecological Study; and to Drs. J. W. Atz, M. R. 

 Carriker, D. M. Pratt, and E. C. Raney, scientific 

 advisors to this study, who reviewed the man- 

 uscript. 



Harold Moody, Florida Fish and Game; Le- 

 Roy Rand, Morris Crab Company; W. C. Stew- 

 art, Florida Power and Light Company; Dr. 

 Jackson Davis, Virginia Institute of Marine Sci- 

 ence; Dr. Theodore R. Rice, NMFS Atlantic Es- 

 tuarine Fisheries Center; William Boyd, Essex 

 Marine Laboratory; and Angelo Baldi, generous- 

 ly provided temperature and catch records for 

 the Atlantic coast rivers. This study was funded 

 in part by the Connecticut River Ecological 

 Study, which was undertaken by the Connecticut 

 Yankee Atomic Power Company in fulfillment of 

 the terms of the construction permit granted by 

 the State of Connecticut Water Resources Com- 

 mission, 21 October, 1964; it was also sup- 



ported by the Connecticut Research Commission 

 (Grant No. R.S.A. 68-19). 



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