Males and females, dropping domistreain and no longer possess- 

 ing the strengiih to sivim against the current, generally moved 

 tail-first tvith weak STvimming movements against the current. 

 Even at this stage, they still retained a positive response to 

 the stream current. 



(6) Adults prevented from spawning 



A preceding discussion considers one possible fate of sea 

 lampreys prevented by barrier dams from reaching suitable 

 spawning areas in streams, i.e., they mijiit spawn on gravel shoals 

 in the lake proper. Such a situation was considered unlilcely. 



There is evidence that a diversion of some individuals of such 

 barred runs to other streams along the shoreline, with accessible 

 spavming areas, occurs. In 19h9, a small, portable weir and trap 

 were operated intermittently in Milligan Creek, Presque Isle 

 County (T37N, R2E, Sees, h, $, 8, 9). This stream is 6.5 miles 

 and 9.0 miles W of Carp Creek and the Ocqueoc River, respectively, 

 on the Lalce Huron shoreline. In each year, 19U7-19U9, it was 

 observed that a run estimated at from 600 to 1,000 sea lampreys 

 entered this stream in the early spring. It was also observed in 

 each year that for some as yet undetermined reason all of these 

 migrants abandoned this stream without spaivning. Conditions ivere 

 comparable, therefore, to those where a mechanical barrier pre- 

 vented access to spawning grounds. 



Ilinety-one sea lampreys were taken in this weir-trap during 

 eight 2l4.-hour periods of operation on l.!ay 1$ and during May 20-26 

 inclusive. Eighty-six individuals were moving upstream and five 

 were moving dovvnstream at the time of captiire. All of these lam- 

 preys Trere tagged with numbered, celluloid button tags and re- 

 leased in the direction in which they were originally traveling 

 (3/8-inch diameter tags; applied Tdth 2 l/2-inch, nickel-plated 

 banlc pins through the dorsal musculature, just anterior to the 

 first dorsal fin). 



Six of these marked sea lampreys (7.0 percent of total tagged) 

 appeared in the Carp Creek and Ocqueoc River weirs. These streams 

 represent the tvro nearest potential spa'vvning streams SE of l£Llligan 

 Creek along the Lal-ce Huron shoreline. One recovery in Carp Creek 

 was taken 10 days after tagging; the five in the Ocqueoc River at 

 2, 6, 10, 17, and 30 days after tagging. 



An additional tagged sea lamprey was recovered in the Macki- 

 naw Straits by a commercial fisherman on, or about, July 1$, 19h9, 

 some 51 days after it had been tagged. It was taken 3 l/2 miles 

 ITE of Mackinaw City in 73 feet 01 water on a mud bottom. The 

 lamprey was caught when its tag became entangled in the twine of 

 a gill-net set. 



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