Table 2. — Young-of-the-year fishes taken in the same trawl hauls as walleyes (1968) 

 [Expressed as percentage of total trawl catches in each Indicated period '; no data for Area 3 because walleyes east of the Islands were taken in large-mesh trawls] 



Dates of capture 



Yellow 

 perch 



Emerald 

 shiner 



Gizzard 



shad 



Alewife 



Spottail 

 shiner 



White 

 bass 



Shceps- 

 bead 



Trout- 

 ixrch 



Smelt 



July 17-24., 

 Aug. 14-16. 

 Oct. 15-18.. 



June 25-27 



July 2-18 



July 25- Aug. 1. 



Aug. 20-30 



Sept. 18-19 



Oct. 29-Nov. 1. 



Extreme western Lake Erie (Area 1) 



39.2 

 16.9 

 66.3 



Island region (Area 2) 



97.1 

 99.0 

 38.8 

 79.6 

 17.9 

 73.0 



4.1 

 2.2 



0.7 

 11.9 

 1.2 



7.4 

 .1 



<0. 1 

 .8 



1.4 

 .6 



0.1 



30.8 

 12.7 

 47.2 

 19.3 



2.5 

 .2 

 16.6 

 4.1 

 13.6 

 .4 



1.1 

 <.l 

 5.9 

 1.9 



0.2 



.4 

 1.0 

 1.9 



0.2 



.1 



.7 



0.2 



<1 



1.2 

 1.5 

 .6 



Numbers of young-of-the-year walleyes caught are given in table 1 and table 4. 



Cent of the total number of fish taken in the trawl 

 (table 2). In contrast, white bass made up 43.4 

 percent of the total number of O-group fish in the 

 trawl catches from which the walleyes were ob- 

 tained but none were found in walleye stomachs. 

 Yellow perch composed 39.2 percent of the trawl 

 catches but were in only 9.0 percent of the stom- 

 achs. The consumption of smelt and spottail 

 shiners was negligible. No emerald shiners had 

 been eaten. 



Gizzard shad and alewives were being sup- 

 planted by other prey in stomachs of walleyes cap- 

 tured August 14-16. The volume of the two 

 species in stomachs had dropped to 40.4 percent 

 and the frequency of occurrence was only 13.9 

 percent for the gizzard shad and 8.3 percent for the 

 alewife. Emerald shiners had entered strongly 

 into the diet; they made up 47.0 percent of the 

 volume and occurred in 47.2 percent of the stom- 

 achs. Emerald shiners were scarce, nevertheless, 

 in trawl catches (0.4 percent of the total catches). 

 The number of gizzard shad and alewives com- 

 bined had increased to 10.9 percent of all fish 

 caught, even though they had decreased in im- 

 portance as food for walleyes. White bass, still 

 the most abundant forage species available, had 

 not been eaten. 



The shift in food from gizzard shad and alewives 

 to emerald shiners was complete in October when 

 the identifiable stomach contents of 32 walleyes 

 contained only emerald shiners. Emerald shiners 

 had increased to 12.4 percent of the total catch 

 of trawls in mid-October. Young-of-the-year 

 yellow perch, although now the most available 

 forage fish (66.3 percent of the total trawl catches), 



FOOD OF YOUNG WALLEYES IN LAKE ERIE 



had not been eaten. Walleyes apparently sought 

 more emerald shiners as the gizzard shad and 

 alewives grew to a size that made them unsuitable 

 prey (table 3). 



Insects were eaten most commonly in August 

 when the percentage frequencies of occurrence of 

 pupae and larvae of the midge Tendipes were 13.9 

 and 2.8 percent, respectively. Tendipes, however, 

 constituted a negligible amount of the total volume 



Table 3. — Comparison of total lengths (mm.) of young-of- 

 the-year fish caught in trawls in extreme western Lake Erie 

 and those taken from walleye stomachs (1962) 



491 



