36 Ted R. Angradi 



specimens collected on separate dates to calculate an approximate growth rate 

 for the medusae. 



METHODS 



I observed the medusae at Wolf Fork (80°28'W, 38°59'N), a cove 

 formed by a flooded tributary to Skin Creek which forms the east arm of 

 Stonewall Jackson Lake (Fig. 1). Wolf Fork is about 1.5-km long and 30-150-m 

 wide and has abundant flooded timber. The cove is well sheltered from winds 

 and is a no-wake boating zone. A culvert connects Wolf Fork and the stream 

 draining the upper watershed. Stonewall Jackson Lake is a 1,070-ha Army 

 Corps of Engineers reservoir filled in 1986. The main West Fork River arm of 

 the reservoir is a tributary of the Tygart River in the Ohio River drainage. 



During my initial visit to Wolf Fork (16 August 1995) I estimated the 

 density (number m 3 ) of medusae using two methods. Where the medusae were 

 abundant I used a 20-L plastic bucket. From a small boat I slipped the bucket 

 into the water and withdrew it with minimal turbulence. I poured the bucket con- 

 tents through a fine sieve and transferred the medusae to a tray for enumeration. 

 Where the medusa were scarce, I estimated the density visually. Both methods 

 are biased toward the upper 0.5 m of water surface because I could not see or 

 sample medusa at greater depths. On the first visit to Wolf Fork I collected water 

 samples and recorded water temperature and dissolved oxygen at several loca- 

 tions in the cove. Water samples were analyzed at the U.S. Forest Service Tim- 

 ber and Watershed Laboratory, Parsons, West Virginia. 



Fig. 1 Map of Stonewall Jackson Lake showing the swarm location at Wolf 

 Fork. Inset map shows location of the reservoir in West Virginia. 



