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Aijiuilic Ecosystems — Our Livnig Resources 



1929-43 average. Stocked lake trout were less 

 important in the restoration of wild lake trout in 

 Wisconsin than in Michigan. Because most 

 spawning reefs in Wisconsin were farther off- 

 shore than in Michigan, they were not found by 

 inexperienced stocked spawners. The increased 

 abundance of wild lake trout in Wisconsin was 

 largely due to reproduction by surviving wild 

 fish in the 1960"sand 1970"s. 



Direct measures of historical abundance do 

 not exist for Minnesota or Ontario. The cunent 

 abundance of lake trout in Minnesota is below 

 that in Michigan and Wisconsin, but in Ontario 

 it is probably similar to Michigan. Lake trout 

 restoration is progressing in Minnesota but is 

 behind that in Michigan or Wisconsin. Patterns 

 of abundance in Minnesota since 1963 are sim- 

 ilar to those in Michigan since 1959. 

 Reproduction by stocked lake trout produced 

 increased abundance of wild lake trout in 

 Minnesota, as in Michigan (Hansen et al. 1995). 

 Progress in lake trout restoration in Ontario is 

 sufficient to elimmate stocking in nu)si areas. 

 Excessive fishery exploitation in the Michigan 

 side of Whitefish Bay caused the deferral of 

 lake trout stocking in the Ontario side. This 

 defeiTal of lake trout restoration will continue 

 until fishery management agencies in Michigan 

 better regulate fishery exploitation. 



Lake trout reestablished self-sustaining pop- 

 ulations in much of Lake Superior, though few 

 have reached former levels of abundance. Still, 

 most of these populations are sufficiently large 

 to support limited commercial and sport fishing. 

 Current or proposed strategies for restoring wild 

 lake trout in Lake Superior include controlling 

 fishery exploitation, reducing sea lamprey pop- 

 ulations, and reducing or eliminating stocking 

 where self-sustaining populations exist. 



Lake Michigan 



Wild lake trout populations collapsed in 

 Lake Michigan during the 1940"s and the 

 species became extiipated in the I950"s (Holey 

 et al. 1995). Stocking began in the 1960"s. The 

 abundance of stocked lake trout increased in the 

 late 1970"s. then decreased in the northern part 

 of the lake because of excessive fishery 

 exploitation. Scattered evidence of lake trout 

 reproduction, including eggs deposited on 

 spawning grounds and newly hatched juvenile 

 lake trout, has been found since the 1970"s. 

 although the only production of wild lake trout 

 more than 1 year old was in Grand Traverse Bay 

 during the late 1970's and early 1980's. 

 Unfortunately, excessive fishery exploitation 

 destroyed the wild lake trout produced in Grand 

 Traverse Bay. preventing the establishment of a 

 self-sustaining population (Holey et al. 1995). 

 Current efforts to restore lake trout to Lake 

 Michigan focus on stocking a variety of lake 



trout strains in offshore refuges that may afford 

 protection from fishery exploitation, allowing 

 restoration of wild populations to occur. 



Lake Huron 



Wild lake trout populations collapsed in 

 Lake Huron in the 1940"s and the species 

 became extirpated in the main basin in the 

 1950's (Eshenroderet al. 1995). Stocking began 

 in the I970"s. Abundance of stocked fish in 

 southern Michigan waters increased steadily 

 during the 197()"s and 1980's. then decreased in 

 response to reduced stocking. Abundance in 

 northern Michigan waters increased briefly dur- 

 ing the late 1970"s and eariy 1980"s. but 

 decreased slowly after that because of excessive 

 sea lamprey predation and fishery exploitation. 



Natural reproduction occuned in Thunder 

 Bay, Michigan, and South Bay, Ontario, but 

 self-sustaining populations have not developed 

 at either location. Restoration efforts now focus 

 on reducing the number of sea lampreys and 

 slocking a variety of lake trout strains on off- 

 shore reefs and in a refuge. The refuge, located 

 in the northern part of the lake, may provide 

 protection from fishery exploitation, and there- 

 by may allow a self-sustaining population to 

 become established. 



Lake Erie 



Wild lake trout populations collapsed in 

 Lake Erie during the 1920's (Cornelius et al. 

 1995). Stocking began in the 1980"s. 

 Abundance of stocked lake trout increased 

 steadily following initial chemical treatment of 

 sea lampreys in 1986-87. although abundance 

 of stocked lake trout decreased after 1990 for 

 unexplained reasons. Cunent restoration efforts 

 focus on controlling sea lampreys and stocking 

 yearling lake trout. Research efforts focus on 

 identifying causes of declining abundance of 

 stocked fish and determining whether adult lake 

 trout will aggregate at suitable spawning loca- 

 tions and reproduce successfully. 



Lake Ontario 



Wild lake trout populations collap,sed in 

 Lake Ontario between 1930 and 1960 (Elrod et 

 al. 1995). Stocking began in the I970"s. 

 Stocked lake trout subsequently survived to 

 maturity, spawned, and deposited eggs that 

 hatched into juveniles. These juveniles, howev- 

 er, evidently did not survive to later ages 

 because fishery biologists have not yet discov- 

 ered any older, wild-origin lake trout. Current 

 restoration efforts focus on stocking strains of 

 lake trout that reproduce most successfully. 

 Research focuses on evaluating factors that 

 limit survival of the fry. such as predation and 

 contaminants. 



