Cottus Life History in Delaware 93 



known, and in March both frequency of sampling and sample size were 

 increased. Surprisingly, no effect of increased collecting on the popula- 

 tion was noted. Although on each collection date the sampling area was 

 almost cleared of specimens, and no additional sculpin could be found, 

 on each subsequent visit the area again was productive. Thus, it appears 

 that many fish escaped capture, or that there was extensive and rapid 

 movement into the sampling area from nearby. Probably both were 

 important. Certainly larval C. bairdi are secretive, which probably 

 explains our failure to catch them at Butler Mill Branch. Hatchlings in 

 the laboratory are benthic to at least 288 hours. When disturbed they are 

 strong swimmers, but then settle rapidly and remain quietly in gravel. 

 This larva-gravel association may explain why C. bairdi is restricted to 

 areas of gravel. 



Further, lower Butler Mill Branch, including all of the sampling 

 area, was poisoned with rotenone in May 1976 by Delaware Division of 

 Fish and Wildlife personnel to foster game fish in Craigs Pond (Roy W. 

 Miller, pers. comm.). Sampling for sculpins in 1978 revealed no effect of 

 the rotenoning. We conclude that the population of C. bairdi here is 

 healthy, and the adjacent Maryland populations also appear to be strong. 



ACKNOWLEDGMENTS.— We thank the following individuals for 

 their help. Johnson C.S. Wang, Nancy J. Bieber, Ruth A. Hermansen, 

 Judith K. Heyman, Michael J. Hozik, Joan A. Pienta, and several Stock- 

 ton State College students assisted in collecting. J. C.S. Wang also exam- 

 ined sculpin eggs, and Michael J. Hozik provided information on geol- 

 ogy. Robert H. Simmons, U.S. D.I. Geological Survey, Water Resources 

 Division, Dover, Delaware, provided stream flow data. Roy W. Miller, 

 Supervisor of Finfisheries, Delaware Division of Fish and Game, Dover, 

 supplied information on rotenoning in Butler Mill Branch. William L. 

 Pflieger, Missouri Department of Conservation, Columbia, provided 

 information on the Ozark populations of C. bairdi. Robbin N. Rogers 

 searched samples for fish eggs and larvae. Bruce W. Menzel and Steve W. 

 Ross made numerous helpful comments during manuscript preparation. 

 Nancy J. Bieber and Deborah K. Wozniak typed drafts of the manus- 

 cript. John E. Cooper and an anonymous reviewer provided helpful 

 comments during manuscript review. 



LITERATURE CITED 

 Bailey, Jack E. 1952. Life history and ecology of the sculpin Cottus bairdi 



punctulatus in southwestern Montana. Copeia 1952(4):243-255. 

 Daiber, Franklin C. 1956. A comparative analysis of the winter feeding habits of 



two benthic stream fishes. Copeia 1956 (3): 141-151. 

 Dineen, Clarence F. 1951. A comparative study of the food habits of Cottus 



bairdi and associated species of Salmonidae. Am. Midi. Nat. 46(3): 640-645. 



