FISHERIES SECTION 



The Fisheries Research Section was made responsible for 

 developing a research position respecting the quality of the 

 environment, and the Supervisor became a member of the 

 Committee on Fisheries and Wildlife Research, Science 

 Council of Canada. 



GREAT LAKES UNITS 



LAKE ONTARIO UNIT 



The sea lamprey population reached its highest level of 

 abundance since the mid 1950s and continued to be a 

 serious impediment to research and management progress. 



The whitefish population continued to show modest 

 signs of improvement under the experimental management 

 system which has reduced exploitation levels. Laboratory 

 studies of whitefish egg and fry survival under adverse en- 

 vironmental conditions, such as those which may now pre- 

 vail in Lake Ontario, are proceeding. 



Sampling stations in the Bay of Quinte were continued to 

 monitor the deterioration of that environment for fish. Sub- 

 stantial areas of water, showing an oxygen depletion in late 

 summer, have now developed. 



Laboratory studies of the effect of DDT on Walleye re- 

 production was conducted in the spring and require repeti- 

 tion in 1971. 



Experimental plantings of splake and kokanee continued 

 in efforts to develop practical rehabilitation plans when sea 

 lamprey control is realized. Lamprey wounding on experi- 

 mental coho plantings were observed to be severe. 



LAKE ERIE UNIT 



Further data on the condition of important fish stocks were 

 obtained by sampling the commercial catches and through 

 the use of experimental gear at a few specific locations. 



The Index Fishing Project, designed to establish by ex- 

 perimental fishing a year-to-year index of the relative 

 abundance of some fish species, provides data for predict- 

 ing, at least qualitatively, the success of commercial fishing 

 one or two years hence. Smelt continue to be abundant, 

 and a strong year class was produced in the spring. Yellow 

 perch reproduction was again poor. 



LAKE HURON UNIT 



The long-awaited beginning of the rehabilitation program 

 for Lake Huron, using the highly selected splake, was begun. 

 The splake, a special hybrid which has been under selective 



development in the Research Branch for some 15 years, has 

 been specifically designed to fit the changed environment 

 of Lake F^uron and is the basic element of the international 

 program^ of rehabilitation now under way in Lake Huron. 

 The first modest plantings were made last year, and the fish 

 will be the object of intensive research to document sur- 

 vival, growth and reproduction in the wild. 



Kokanee studies continue to provide grounds for optim- 

 ism that this salmon species may meet our expectations. 

 Natural reproduction by planted stocks has now been re- 

 corded in both streams and on shoals. 



Whitefish studies, which are now concentrated on the 

 formerly little known, early life history stages, show promise 

 of (a) possibilities of developing index stations where we 

 may predict whitefish abundance four or five years earlier, 

 and (b) possibilities of understanding the factors which 

 determine year-class strength and subsequent population 

 size. 



LAKE SUPERIOR UNIT 



Significant numbers of native, undersized lake trout have 

 finally made an appearance in the catches presumably as a 

 result of the apparently meagre spawning of the past two 

 years. There is evidence of a minor decrease in lamprey 

 activity generally, although some areas show sharp in- 

 creases. Adequate data are now available from research 

 to provide an opportunity to reassess the major planting 

 program. 



In relation to an ecological study of rainbow trout, timno- 

 logical data from Batchawana Bay and Carp and Stokely 

 streams were gathered. A distribution study indicated that 

 these fish were most abundant near shore in shallow water. 



GAME FISH UNITS 



LAKE TROUT UNIT 



The creel census in operation since 1935 is continuing to 

 provide information on the dynamics of populations. Work 

 has started on a Lake Trout Monograph which is intended 

 to bring together in one volume all information on this 

 species. A major report on the effect of food habits on the 

 biology of lake trout was issued this year. 



BROOK TROUT UNIT 



Emphasis has been on improving the contribution of 

 planted stocks to anglers' catches. Natural and planted popu- 

 lations are being studied for background information. 

 Studies include population sizes and a measure of the yield 

 under different levels of fishing intensity. 



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