Two papers, "Long term effects of diet on the biology of 

 the lake trout and the fishing in Lake Opeongo, Ontario" 

 and "Trophic-dynamics of lake trout production systems," 

 were published. 



A master map has been prepared showing the distribution 

 of the lake trout in Ontario on a lakel by-lake basis for both 

 native and introduced populations. 



BROOK TROUT UNIT 



This program consists of studies on two natural lake popula- 

 tions and an assessment of the survival of hatchery reared 

 fish in 18 lakes which lack natural brook trout reproduction. 



A manuscript has been completed describing the survival 

 of salmonids in six lakes. It shows that lakes with fewest 

 resident species yielded a higher return than those with 

 more complex populations. Planted splake and rainbow 

 generally yielded higher returns than brook trout. 



The low survival of planted fish was apparently the result 

 of competition by resident fish species and predation by 

 wild trout and fish-eating birds and mammals. 



Studies on planting methods indicate that air-dropped 

 fish survive better when dropped into shallow water rather 

 than deep water, but hand planting is superior to air drops 

 in terms of survival. 



Preliminary results of an investigation into the feasibility 

 of winter stocking show that the recovery of spring planted 

 fish was considerably greater than from fall and winter 

 plantings. 



Other experimental work involved artificial spawning 

 facilities and attempts to condition young trout to avoid 

 predators in the early stages of their introduction by 

 planting. 



SMALLMOUTH BASS 



Studies were conducted to determine the existence of rela- 

 tionships between such things as nest success, number of 

 eggs and fry, and variability of year class. 



Creel census data suggest that the bass population in 

 Lake Opeongo are undergoing a growth rate change that 

 might result in a stunted population. Studies are continuing 

 to determine the cause and possible technique to reverse 

 this trend. 



Observations, made directly and indirectly of the life 

 history, ecology and behaviour of bass, revealed sampling 

 problems such as fish that, once trapped, return to the trap 

 by preference, or those that refuse to enter a net, and the 

 varied reactions of the fish to angling equipment in general. 



A study of the yearly life cycle of bass by direct under- 

 water observation revealed the largest fish left the rock caves 

 in which they spent the winter in late April and early May. 

 All bass were out and feeding by the end of June. By mid- 

 May, most adults were cruising the lakes and taking part in 

 limited pairing. Males began nest preparation in late May on 

 gravel bottoms, usually near logs or large boulders. Court- 

 ship and spawning began at the end of May. Egg care by the 

 male is minimal, but nest guarding continued throughout 

 the night. Egg predation was limited but logperch persist- 

 ently preyed on larvae. The young of the year moved to 

 shallow water, and in late summer at about 2" in length 

 started schooling. As fall approached, adults and sub-adults 

 moved into deeper water and hid in rock caves. 



Sublimnos, the underwater research platform, continued 

 to provide a habitat for underwater studies. These included 

 under-ice observations carried on throughout the winter. 



A study was initiated to determine the nature of the prob- 

 lem of potential oil spills in the Great Lakes in response to 

 appointment to a contingency force to clean up the effects 

 of such an event. 



WALLEYE UNIT 



A study on water transparency explains why walleye are 

 much more vulnerable to daytime angling in lakes with low 

 transparency levels than those with high levels. 



A complementary study of the influence of varying light 

 intensity on walleye behaviour, especially feeding, was con- 

 cluded and reported. 



A co-operative project with the Fisheries Research Board 

 of Canada, to identify different phenotypes of walleyes 

 through electrophoretic examination, was completed and 

 a report published. 



A bibliography of about 2,100 citations concerning the 

 walleye, sauger and blue pike has been completed and sub- 

 mitted for publication. 



DISCIPLINE UNITS 



LIMNOLOGY UNIT 



The study of small lakes and ponds was expanded to include 

 a study of the higher aquatic plants, phytoplankton, and a 

 wider range of chemical characteristics. The inclusion of 

 the higher aquatic plants is to relate their distribution and 

 abundance to the physical and chemical properties of the 

 respective waters and to the extent of eutrophication. It is 

 hoped that indicator species may be recognized. 



Attempts to relate water chemistry and degree of eutro- 



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