in assessing data from untrained observers. A salmonid 

 identification criteria table has been developed. 



A review of the Japanese salmon suggests that the species 

 offers considerable potential as a new/ species for Ontario. 



A short paper describes some of the details of incubating 

 walleye eggs and their thermal unit requirements. 



The upper lethal temperature among young-of-the-year 

 walleye was again examined with results closely paralleling 

 those of the previous year. 



Environmental monitoring observations showed in general 

 that average values for chlorophyll and inactive chlorophyll 

 or phaeo pigment, ammonia nitrogen, nitrate and nitrite 

 nitrogen, phosphate, detergents changed little from earlier 

 values. 



The results of a synoptic survey of oxygen content of Bay 

 of Quinte water from Belleville to Picton confirm advanced 

 eutrophication. A relatively large volume of water along the 

 bottom of the Bay of Quinte was found to be seriously 

 depleted of oxygen. The assessment of fish stocks indicated 

 that yellow perch maintained its relative position, but that 

 walleye reached an almost record low. 



A paper, entitled "The American Eel in Eastern Lake 

 Ontario," reveals that eels enter the lake at age 6-8 years 

 where they remain for up to 20 years before returning to the 

 sea to spawn and die. 



Comprehensive investigations, involving the standing crop 

 of fish in Shelter Valley Creek, provided the data on which 

 it is proposed to produce an energy budget and to test 

 various experimental techniques for their effectiveness in 

 manipulating the system. 



LAKE ERIE UNIT 



Fish stock monitoring, using index fishing and net-run 

 sampling techniques, showed a decline in smelt catches as 

 well as yellow perch. Since next year's catch will depend 

 largely upon the same year classes, it is anticipated that it 

 will be no better and possibly smaller. 



Limnological studies were initiated in the western basin 

 of Lake Erie and Lake St. Clair in support of the fisheries 

 programs. 



Three inshore and three offshore stations in Pigeon Bay 

 were selected for fortnightly sampling. Visibility values and 

 temperature profiles were obtained at each station. Plankton 

 was sampled, and phytoplankton quantity estimated. Water 

 samples for nutrient, pigment and particulate organic carbon 

 analyses were collected from near-bottom, mid-depth and 

 near-surface of each station. 



Ten stations were selected in Ontario waters ot Lake St. 

 Clair for fortnightly sampling. Two tributary stations were 

 located on St. Clair River and the Thames River. Data col- 

 lected were similar to those collected in Lake Erie. 



Studies of various aspects of the walleye population in the 

 Thames River, Lake St. Clair and western Lake Erie were re- 

 organized and expanded. A number of potential spawning 

 locations, as characterized by gravel bottoms and fast flow, 

 were mapped. 



LAKE HURON UNIT 



The program embraces two broad, major catagories: 

 monitoring programs, in which the gross changes in species 

 composition are .measured; and research programs, in which 

 specific species of special importance to man are studied 

 in greater detail than the monitoring programs provide. 



Results of pound net experimental fishing in South Bay 

 document the following major trends. 



The alewife began its invasion in 1951 and increased 

 dramatically to a peak in 1964. This was followed by a de- 

 cline until 1968. Catches in 1972 and 1973 are expected to 

 show a marked increase since both 1969 and 1970 hatches 

 appear to have been unusually abundant. 



Whitefish catches have shown less fluctuation in abund- 

 ance than any other common species. Fluctuations that have 

 occurred have tended to compensate one another to pro- 

 duce the most stable level in the history of the fishery. A 

 32 per cent increase in catch over the previous year was 

 due to the abundant 1968 year class and may reflect a re- 

 duced level of lamprey abundance. 



Cisco catches were down considerably. Cisco were ob- 

 served to be feeding on young smelt rather than alewives as 

 previously observed. 



Yellow perch catches were the lowest on record. 



White sucker catches have fluctuated less than other 

 abundant species. Catches were considerably higher than 

 the previous year which had been very low. 



Splake and kokanee catches were down by 82 and 97 per 

 cent, respectively. 



South Bay Smelt Index Stations showed a slight increase 

 in smelt abundance over the previous year. Adult alewife 

 and kokanee catches were markedly down, while splake 

 increased due to the catch of yearlings from a planting 

 earlier in the year. Whitefish declined, while white sucker 

 continued to increase steadily. 



90 



