Bottom Trawl Explorations in Lake Superior, 



1963-65 



By 



NORMAN J. REIGLE, JR., Fishery Biologist 



Bureau of Commercial Fisheries 



Exploratory Fishing and Gear Research Base 



Ann Arbor, Mich. 48103 



ABSTRACT 



Six exploratory fishing cruises, totaling 122 operating days, were made by the 

 research vessel Kaho from November 1963 toOctober 1965. Most of the exploratory 

 operations were in the central and eastern portions of the lake; however, limited 

 surveys were made in the western area during 1965. This study is the first attempt 

 to assess the potential for commercial bottom trawling in Lake Superior. 



Suitable bottom for trawling was found along about 65 percent of the south shore. 

 Over 74 percent of the total catch by the Kaho were chubs ( Leucichthys spp.) fol- 

 lowed by American smelt ( Osmerus mordax ), 10 percent; suckers ( Catostomus spp.), 

 6.5 percent; and lake trout ( Salvelinus namaycush ), 3 percent. Commercially signif- 

 icant catches, 250 pounds per one -half hour, of chubs were taken on every cruise and 

 these fish, even if used mainly for animal food products, could apparently support a 

 limited trawl fishery. Smelt, suckers, and common whitefish ( Coregonus clupea- 

 formis) were caught occasionally in commercially significant quantities and could 

 greatly supplement production efforts. Most lake trout were caught in specific 

 geographic areas and appeared to be segregated by size in specific depth zones. 

 Abundant concentrations of small trout could easily be avoided after being located by 

 fishing certain depths. With proper care, most trout were returned to the water 

 alive. The alewife ( Alosa pseudoharengus ), which is now the basis of a growing trawl 

 fishery in Lake Michigan, and lake herring ( Leucichthys artedi) were not taken in 

 significant amounts during the study. 



INTRODUCTION 



The commercial fishery of Lake Superior 

 has been declining since the mid-1950's. The 

 decline is attributed primarily to the sea 

 lamprey, which almost destroyed the popula- 

 tions of lake trout and whitefish. 



Fishing gear and methods that were satis- 

 factory for catching large and valuable fish 

 are not satisfactory for taking the small and 

 low-valued fish that are available today. Some 

 species, such as American smelt, cannot be 

 profitably taken by traditional methods (pound 

 nets) except during their spawning season. 

 Other abundant species, such as bloater chubs 

 (Leucichthys hoyi), which are now used for 

 animal food, cannot be caught efficiently enough 

 by traditional methods (gill nets) for profitable 

 operations. 



To investigate current problems and provide 

 advisory services to the commercial fishery 

 sector of the Lake Superior economy, a 

 technical assistance project was established 

 under the Area Redevelopment Administration 

 (now the Economic Development Administra- 



tion). A basic study phase of the project was 

 in effect from April 1964 to September 1965. 

 One part of this study was to determine the 

 seasonal abundance and distribution patterns 

 of important species a s related to their 

 availability to effective and economical fishing 

 methods. This report summarizes four ex- 

 ploratory cruises that were made under this 

 project and two additional cruises that were 

 made in support of the investigation. 



Bottom trawling was chosen as the primary 

 fishing method because of its proven ability 

 in the Great Lakes and elsewhere to sample 

 fish that spend all or most of their time in 

 bottom waters. Trawling has long been a com- 

 mon method for surveying fishery resources 

 and for catching a wide variety of species. 



The Bureau of Commercial Fisheries re- 

 search vessel Kaho operated 122 days on 

 Lake Superior during six cruises. Bottom 

 trawl explorations began in the Whitefish Bay 

 area during November 1963. In 1964 three 

 additional cruises were nnade: (1) in late 

 May through early June, (2) August, and (3) 

 November through early December. During 



