In northern Lake Huron, chubs have shown a steady 

 decline. 



Earlier studies of whitefish, revealing the marked parallel- 

 ism in the annual abundance indices tor sac fry, for young 

 whitefish and for older age groups, suggest that the general 

 level of year class abundance is established early in the life 

 history of whitefish. Correlation studies also suggest climatic 

 conditions during incubation and hatching may be influen- 

 tial in establishing year class strength. 



Consequently, studies were initiated to attempt to learn 

 what factors are contributing to mortality of whitefish eggs. 

 Initial trials, using mathematical models to simulate the im- 

 pact of factors affecting whitefish production, were under- 

 taken. The over-all conclusion from the studies was that 

 mortality reduction is the most important goal a fisheries 

 manager can strive for in attempting to conserve an ex- 

 ploited whitefish fishery. 



A splake study in South Bay is dealing with the detailed 

 life history and population dynamics of highly selected 

 splake. Included are survival, reproducitve success and tem- 

 poral and spatial distribution. The high proportion of mature 

 yearling females caught in shoal gillnets suggests that a 

 substantial egg disposition might occur as early as 1971. 



The smallmouth bass fishery is expected to show improve- 

 ment in the next two years because of strong 1968-70 year 

 classes. 



Taking eggs from a Georgian Bay feofcanee. Photo by VV. D. 

 Marshall. 



1 ^ 



LAKE SUPERIOR UNIT 



The main objectives have been the development, refinement 

 and application of methods for assessing the success of the 

 sea lamprey program and the provision of an increasingly 

 precise and detailed accounting of the response of depleted 

 fish stocks, especially lake trout, to the fishery management 

 measures taken on their behalf. 



The existance of significant qualities of mercury in lake 

 trout has had considerable impact upon the sampling pro- 

 gram since commercial fishermen have diverted attention to 

 other species. 



A report, "Life history of rainbow trout in Batchewana 

 Bay, eastern Lake Superior," based on a two-year study, vvas 

 produced. 



Considerable effort has been expended in determining the 

 best possible manner in which the extensive amounts of data 

 required for this type of program can be processed. 



CAME FISH UNITS 



HARKNESS LABORATORY UNIT 



A full-time director was provided with duties that include 

 completion of earlier research assignments, development of 

 new projects appropriate to the Laboratory, and the respon- 

 sibility for the conduct of projects which are parts of the 

 programs of other research units which make data collection 

 demands on laboratory staff. Another major responsibility is 

 the co-ordination of the activities of the several co-operative 

 research agencies and individuals who use the laboratory. 



A study was undertaken to assess the recovery of benthic 

 populations in lakes treated with fish toxicants as part of a 

 lakes reclamation program. 



Biological and harvest data were obtained for the Lake 

 Trout Unit, Smallmouth Bass Unit and Brook Trout Unit, 

 while appropriate services were provided for the Parasit- 

 ology Unit. 



Demands of co-operative research projects in terms of 

 accommodation, equipment and professional support were 

 again substantial, and special programs were prepared for 

 various visiting classes. 



LAKE TROUT UNIT 



Lake Opeongo census studies reveal that although the fish- 

 ery has been variable, in terms of harvest and availability of 

 the trout, it has remained relatively stable for about the last 

 20 years. It appears capable of sustaining an annual harvest 

 over the long term of from 1,000 to 1,500 trout per year and 

 a yield of 13 pounds per acre. 



91 



