Thermal Preferenda and Diel Activity Patterns 



of Fishes from Lake Waccamaw 



W. W. Reynolds and M. E. Casterlin 



Biothermal Research Institute 

 R. D. 3, Box 10, Wyoming, Pennsylvania 18644 



and 



D. G. LlNDQUIST ' 



Department of Biology 

 University of North Carolina, Wilmington, North Carolina 28406 



ABSTRACT.— We tested seven fish species from Lake Waccamaw in 

 Ichthyotron electronic shuttleboxes to determine their preferred temper- 

 atures and diel activity patterns. All preferred temperatures between 

 25 ° and 31 ° C, which corresponded to water temperatures measured in 

 the lake in August 198 1 . All species avoided temperatures below 20 ° or 

 above 36° C. One species was diurnal, two were nocturnal, and four 

 were crepuscular in diel activity pattern under the LD 14:10 August 

 photoperiod. 



INTRODUCTION 



Lake Waccamaw, North Carolina, is one of the shallow "bay lakes" 

 of the southeastern coastal plain of North America. It is unusual among 

 these lakes in having significant calcareous buffering capacity, and thus a 

 pH normally at or above neutrality. Another unusual feature of Lake 

 Waccamaw is that it harbors three endemic fish species: Fundulus wac- 

 camensis Hubbs & Raney, the Waccamaw killifish (Cyprinodontidae); 

 Menidia extensa Hubbs & Raney, the Waccamaw silverside (Atherini- 

 dae); and Ethe o stoma per longum (Hubbs & Raney), the Waccamaw dar- 

 ter (Percidae, Etheostomatinae). An undescribed ictalurid, Noturus sp., 

 the broadtail madtom, also occurs in the lake. 



In connection with a survey to assess the conservation status of the 

 endemic species, we measured the thermoregulatory behavior (preferred 

 and avoided temperatures) and diel activity patterns of several fish spe- 

 cies. They included the three endemic and one undescribed species named 

 above, and three others that had never been so tested — Lepomis margina- 

 tus (Holbrook), the dollar sunfish (Centrarchidae); Enneacanthus chae- 

 todon (Baird), the blackbanded sunfish (Centrarchidae); and Noturus 

 gyrinus (Mitchell), the tadpole madtom (Ictaluridae). 



1 Direct reprint requests to DGL 



Brimleyana No. 7:55-60. July 198 1 . 55 



