McCabe and Tracy: Spawning and early life history of Aapenser transmontanus 



769 



sturgeon were found was predominantly sand; how- 

 ever, much of the bottom in the lower Columbia River 

 is composed of sand. In addition, the bottom trawls 

 could not be used in rocky areas. 



During the 20-hour sampling survey from 31 July 

 to 1 August 1990 (sampled from 1155 through 0800 

 hours) at rkm 75, 52 YOY white sturgeon were col- 

 lected (Table 6). Over 78% of YOY white sturgeon 

 were collected during hours of darkness, indicating 

 that they were more vulnerable to the trawl at night 

 or that they moved into the sampling area at night. 

 The YOY were collected at depths that ranged from 

 11 to 15 m. 



Discussion 



White sturgeon successfully spawned in the lower 

 Columbia River in all years of the study. All white 



sturgeon eggs collected downstream from Bonneville 

 Dam were probably released by sturgeon spawning 

 in this area and not by sturgeon spawning in the 

 impoundment created by Bonneville Dam. Although 

 white sturgeon spawn in the impoundment upstream 

 from Bonneville Dam (Miller et al. 4 ), it is unlikely 

 that any of these eggs are carried through Bonneville 

 Dam. In 1990, Miller et al. 4 collected white sturgeon 

 eggs between rkm 298 and 308. The locations of white 

 sturgeon egg collections upstream from Bonneville 



4 Miller, A. I., P. J. Anders, M. J. Parsley, C. R. Spraque, J. J. 

 Warren, and L. G. Beckman. 1991. Report C. In A. A. Nigro 

 (ed.). Status and habitat requirements of the white sturgeon 

 populations in the Columbia River downstream from McNary 

 Dam, p. 82-144. Ann. Rep. to Bonneville Power Admin. (Project 

 86-50) by Oreg. Dep. Fish Wildl., Wash. Dep. Fish., Natl. Mar. 

 Fish. Serv, and U.S. Fish Wildl. Serv. Avail. Bonneville Power 

 Admin., P.O. Box 3621, Portland, OR 97208. 



