vessel M.V. Keenosay, in co-operation with vessels from the States of Ohio and 

 Pennsylvania, the U.S. Bureau of Commercial Fisheries and the Great Lakes 

 Institute, was repeated to map the oxygen depletion zone of water in the central 

 basin of Lake Erie. This oxygen depletion is considered of direct significance 

 to fish populations, and is thought by many to be related to pollution or over- 

 enrichment of the lake. 



Lake Ontario 



A major phase of the long term study of whitefish in Lake Ontario was 

 completed during 1961. A fully documented report is currently being issued. This 

 part of the study was concerned with an accurate assessment of the contribution 

 to the commercial harvest, of hatchery plantings of eyed eggs or fry of whitefish. 

 The conclusions, in brief, are as follows: 



L The planted fry were not sufficiently numerous and/or did not survive well 

 enough to have a sustaining effect on subsequent catches of the fishery. 



2. The fluctuations of year class strength in whitefish in this area seem to be 

 related to the weather. Cool fall spawning periods, followed by warm hatching 

 periods, tend to produce large year classes, and the reverse conditions are 

 associated with the production of smaller year classes. 



3. In those years when weather conditions are unfavourable it appears that 

 the size of the spawning stock and of the fry plantings may influence the size 

 of the fishery for whitefish at five years of age and older. 



4. Large plantings of fry were directly related to the years when spawning 

 stock density was high — ^^that is, it was easy to get eggs when there was an 

 abundance of spawners. 



5. Fry plantings were apparently of no value to the fishery in years when 

 conditions were favourable for natural reproduction. 



6. In years when conditions are unfavourable for natural reproduction, and 

 when spawning stocks are low, the Qgg collection and subsequent fry plantings 

 are low. Even under the best planting and survival conditions the contribution 

 of plantings to the subsequent fishery appear uneconomical. 



Two other major items of information have arisen from this work on white- 

 fish. The fishing eff'ort has increased through the years, primarily through the 

 introduction of nylon twine, and the age composition of the catch has gone down. 

 Even though the industry is using inefficient gear, by net size selectivity standards, 

 the effort has apparently been adequate to cause, in some years at least, a situation 

 of marginal escapement to spawning. A reduction of fishing effort by some 

 method may be necessary to the continuation of the fishery. The other item of 

 immediate interest is the fact that the 1957 year class of whitefish, which was 

 responsible for a great increase in the 1961 commercial catch, appeared in 

 numbers in the falls of both 1960 and 1961 on the spawning grounds along the 

 south shore of Prince Edward County, rather than in the Bay of Quinte, the more 

 usual spawning location. The reasons for this shift of spawning location are not 

 understood, but it is hoped that progeny from the 1961 spawning, when good 

 numbers of females of this year class were mature for the first time, augurs 

 well for the fishery in 1965. 



The commercial catch of lake trout in Lake Ontario again was made up 

 almost entirely of stocks planted by the State of New York and the Ontario 

 Department of Lands and Forests. The commercial catch of trout, while it was 

 at a level consistent with catches incidental to whitefish fishing, were such that 

 they provided a valuable and, from our point of view, economical method of 

 assessing survival of stocks. During 1960, however, and again in 1961, there 



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