LAKE HURON 



The several separate whitefish populations in Lake Huron, Georgian Bay, 

 North Channel and South Bay were sampled as in the past. This sampling program 

 and subsequent age determinations from the scales allows determination of the 

 relative strengths of year classes of whitefish produced in the various areas, and is 

 an essential part of our long-term search for the causes of fluctuations in abundance. 

 The correlation between year class strength and the combined fall-spring tempera- 

 ture index discovered for Lake Ontario whitefish was tested against Lake 

 Huron population fluctuations, but was found invalid. It is apparent that for 

 Lake Huron whitefish, these factors are not limiting or at least some other factor, 

 as yet not recognized, is also influencing year class success. The study will continue 

 until the factors are identified and until we understand how they work. 



Since much of our data and analysis is dependent upon precise age deter- 

 mination, and since this is such a difficult task, work designed to verify and to 

 improve confidence in our ability to age fish from scale samples has been increased. 

 Whitefish and other species are being injected with tetracycline hydrochloride to 

 put a time mark on the scales. Injected fish are tagged for later recognition and 

 released. Subsequent scale samples from these fish have a visible time reference 

 point which helps greatly in the interpretation of age from the scale markings. 



The year class composition of the South Bay smelt population is being studied 

 to determine the effects of fishing pressure. For several years, during the 1950 

 decade, spawning runs of smelt were fished as hard as our facilities would allow. 

 In recent years, there has been virtually no fishing, only sampling. A report covering 

 the quite marked differences between the fished and unfished smelt year classes will 

 be issued shortly and should contribute to our understanding of the effect of fishing 

 on fish populations in general. 



Studies of bass year class strength, of the survival of planted hybrids and of 

 the overall fish population changes in South Bay and Georgian Bay were continued. 

 Co-operative arrangements with the Great Lakes Institute resulted in progress on 

 hydrographic studies in which we have interest. 



LAKE ERIE 



All available data on walleyes were summarized and reported to the Depart- 

 ment and to the Great Lakes Fishery Commission in 1963. These included an 

 analysis of commercial catches and a partial documentation of fishing effort during 

 the 1950 decade when the catches reached an all time high, then fluctuated violently 

 and virtually collapsed. The available age composition and tagging study results 

 were also included. These data were combined with similar U.S. data and with 

 information on changes in water quality in other aspects of the environment, and 

 an integrated report was issued. The controversy which developed concerning the 

 management implications of the information emphasizes the need to expand the 

 Lake Erie's research program to include long-term studies of this species. 



Studies of smelt were continued. The seasonal distribution of this species 

 throughout the lake is now better defined, as are the areas of concentration where 

 most of the fishing effort is directed. No major concentrations, not already 

 discovered by fishermen, were found. Work was begun on an attempt to determine 

 whether or not there are distinct smelt populations in the lake or whether we can 

 consider the smelt as being one large population. The wide variation in smelt 

 spawning time between different areas of the lake shore suggest the possibiliiy of 

 separate populations. Food studies were directed particularly towards the disrovery 

 of cannibalism by yearling smelt, in an effort to explain the phenomenon of altcr- 



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