were terminated early due to gear damage or to 

 avoid bottom obstacles and gill nets. 



Cruise 36 (the final cruise included in this study) 

 covered the 20 days from 12 October to 31 October 

 1966. Forty-seven exploratory drags were com- 

 pleted, six of which were terminated early due to 

 gear damage, gear malfunction, or total loss of the 

 trawl. 



The combined effort (245 drags used here) of all 

 four exploratory cruises was distributed among the 

 three basins of Lake Erie as follows: 



The Western Basin is separated from the Central 

 Basin by an imaginary line connecting the tip of 

 Point Pelee, Ontario, and the tip of Cedar Point, 

 Ohio. The Eastern Basin begins at an imaginary line 

 connecting the base of Long Point, Ontario, and the 

 base of Presque Isle, Pa. (Fig. 4). A summary of all 

 drags by basin appears in Appendix Tables 1 

 through 3. 



SPECIES COMPOSITION OF TRAWL 

 CATCHES 



Results obtained from the data collected during 

 the Lake Erie explorations serve to point out by 

 basin and year the relative shift in species composi- 

 tion from 1962 to 1966 (Fig. 5). Appendix Tables 4 

 through 7 indicate species composition duringeach of 

 the four cruises discussed in this paper. 



The exceptionally good hatch of yellow perch in 

 1959 was evidently responsible for the dominance 

 of this species in the 1962 and 1963 trawl catches 

 (U.S. Fish and Wildlife Service, Region 4, 1966). 

 Alewives were not taken in trawl catches at all dur- 

 ing Cruise 2 (1962) and only in modest quantities 

 during Cruises 4 (1962) and 11 (1963). In 1966, how- 

 ever, during Cruise 36, a sizable population was 

 evident — alewives, Alosa pseudoharengus , ac- 

 counted for 54.4% of the total catch. Rainbow 

 smelt was the second most abundant species during 

 each of the four cruises. Though smelt accounted 

 for 34.4% of the total trawl catch during Cruise 4 

 (1962), in October of 1966, during Cruise 36, smelt 

 accounted for only 23.9% of the total catch (Fig. 6). 



statute miles 



Figure 4. — Map of Lake Erie showing basins and geographic locations mentioned throughout text. 



