Y ear Number trapped 



!9hS 25 



19U6 125 



19U7 596 



19U8 989 



19h9 1,579 



1950 5,U22 



Whether or not the sea lamprey had reached the peak of its abundance in Lake 

 Michigan will not be revealed until the conclusion 1 of the 195l season. Judging, 

 however, by the rate of decline of the lake trout (an apparently preferred prey 

 species) in this lake, the time when the demand for food far exceeds the supply 

 is fast approaching. 



Lake Superior .— In Lake Superior, stream survey reports and records of occur - 

 rence in the Lake proper indicate that the lamprey is more firmly entrenched than 

 heretofore suspected and, although still not numerous, is on the increase. The 

 presence of spawning runs in streams tributary to the southeastern area of the lake 

 is definitely established. Adults have been captured throughout the lake to its 

 extreme western end. In August 1950, representatives of the Minnesota Conservation 

 Department captured mature spawning migrants in several streams in the vicinity of 

 Duluth, Minnisota. 



Further expansion of the sea lamprey population in Lake Superior may be 

 anticipated. Although adult sea lampreys or their nests were found in slightly 

 less than 10 percent of the 325 streams on the southeastern shore of the lake 

 examined in 1950, rougMy one-third' of the streams in the area are' of a character 

 suitable for sea lamprey reproduction, h/ Utilization of these watersheds by 

 the lamprey may be expected in the near future if the characteristic rate of 

 increase of the species after establishment in a new water (as evidenced in Lakes 

 Huron and Michigan) is displayed. 



Other species of fish taken in weirs and traps and degree of scarring 



among them 



Counts by species were made of fish in 10 of the weirs and traps in Control Zone 

 H-l in northern Lake Huron and in Pendill's Creek which flows into Lake Superior. 

 A total of 103,5Uii fish were taken along with the sea lampreys in the 10 streams 

 of Zone H-l; in Pendill's Creek, 1,2U3 were captured (Table2). Data were collected 

 also on the numbers of lamprey-scarred suckers of several species taken in eight 

 of the streams in Zone H-l and in Pendill's Creek (Table! 3). Scarring records 

 for other species were incomplete. The data presented in this section not only 

 reflect the continuing decline of certain species but also contain a hint that 

 the balance among the remaining fish stocks in this area of Lake Huron may have 

 been profoundly affected by the sea lamprey. 



h/ A detailed report of a survey of streams tributary to Lake Superior which was 

 conducted in 1950 is now in preparation. 



