Table 5. — Species composition of 798 exploratory trawl catches in southern Lake Michigan, 1962-65 



^ T = Trace, less than 0.5 or 0.05. 



Figure 3. — Species composition of exploratory trawl catches by year In southern Lake Michigan. The 1960 data are from 



Gordon (1963). 



percentage differences occurred in 1962 for 

 snnelt and in 1965 for sculpins. These changes, 

 however, do not necessarily represent any 

 biological change. The high percentage of 

 smelt in 1962 was likely the result of two 

 factors: (1) two unusually good catches of 

 340 and 450 pound* and (2)a 65 percent greater 

 fishing effort in tb« depths of 1 5 to 25 fathoms 

 where two-third* of the total poundage of 



snnelt were taken during this study. The catch 

 rate of snnelt at 15 to 25 fathon-is was similar 

 for all years. The high percentage of sculpins 

 in 1965 was a result of greater trawling effort 

 in water deeper than 45 fathoms. 



Because of the pronounced seasonal move- 

 ments of alewives and some movement by 

 chubs, the species composition by depth zones 

 differed for each quarter of the year (table 7). 



