of these runs, when they enter the lake some years hence, will be numer- 

 ous. Further surveys of tributaries of the lake conducted in 19^1 indi- 

 cate that extensive^ but as yet unused, spawning grounds of something less 

 than optimum quality exist for the species at least on the south shore of 

 the lake. A considerable expansion of the population, therefore, appears 

 imminent. Adequate warning of the effects of such an expansion upon the 

 lake trout and other commercially valuable species in the lake may be 

 found in the present condition of fish stocks in Lakes Huron and Michigan. 



Other species of fish taken in weirs and traps 

 and degree of scarring among them 



Counts by species were made of fish entering 10 of the weirs and 

 traps in Control Zone H-1 and in Pendill's Creek which flows into Lake 

 Superior. In addition to the sea lampreys captured, a total of 79,091 

 fish was taken in 10 streams in Control Zone H-I3 307 fish were captured 

 in Pendill's Creek (table I4) . Data were also collected on the numbers 

 of lamprey-scarred suckers of several species taken in 7 streams in Zone 

 H-1 (table 5) . Records of scarring were collected for other food and 

 game species but these records were generally incomplete or based on too 

 few individuals to warrant inclusion here. 



From the data available it is difficult to say whether the food and 

 game species are still declining in northwestern Lake Huron. Trap records 

 indicate a stabilized condiLion might have been reached. 3_/ However, com- 

 mercial fishermen report that fewer suckers and other food species were 

 taken in their nets in 19^1 as compared with 1950. Furthermore, the inci- 

 dence of scarring at least among the suckers, continues to rise. For 

 example^ in 195l, 3U.6 percent of the suckers entering the Ocqueoc trap, 

 as well as those collected in o\ir nets, were scarred. This compares with 

 30.0 percent in 19^0 and 25«5 percent in 19ii9 = 



Some biological characteristics of the 

 sea lamprey runs 



Nearly all of the sea lampreys taken in eight streams in Control 

 Zone H-1 were examined to detennine the sex of the individuals (table 6); 

 similar records were made for all sea lampreys entering one tributary of 

 Lake Suoerior, Examination of these data collected in 19^1 indicates 

 that the sex ratio of entire runs in northern Lake Huron continues to 



3/ It might be observed here that any further decline of, for example, the 

 "suckers below the levels indicated by the weir and trap catches in the pre- 

 ceding year^ 19^0, would have required the near disappearance of this 

 species from adjacent areas of the lake; see Applegate and Smith (195l) • 



