Bottom Trawl Explorotions in Southern Lake Michigan, 



1962-65 



By 



NORMAN J. REIGLE, JR., Fishery Biologist 



Bureau of Commercial Fisheries 



Exploratory Fishing and Gear Research Base 



Ann Arbor, Mich. 48103 



ABSTRACT 



For 4 years the Bureau of Commercial Fisheries Exploratory Fishing and 

 Gear Research Base at Ann Arbor, Mich., surveyed the abundance, seasonal 

 availability, and depth distribution of various fish stocks. 



The alewife (Alosa pseudoharengus) and chubs ( Leucichthys spp.) were taken 

 readily with the bottom trawl. Alewives composed 51.4 percent and chubs 44.0 

 percent of the trawl catch. Two other commercial species, yellow perch ( Perca 

 flavescens ) and smelt ( Osmerus mordax ), were taken occasionally in commercial 

 amounts. 



The alewife stocks have increased tremendously in recent years. The poundage 

 of alewives in the trawl catch increased each year from 17 percent in 1962 to 74 

 percent in 1965. Alewives exhibited pronounced seasonal moven-ients and generally 

 were available to bottom trawls only at specific depths. The trawls caught alewives 

 at depths of less than 5 fathoms to over 50 fathoms. Alewives appeared to be 

 distributed universally in the study area during most of the year but were found only 

 in some sections in winter. Alewives were nnore difficult to catch between July and 

 the end of December than during January through June. 



Chubs were abundant all year throughout southern Lake Michigan. Chubs were 

 caught over a wide depth range throughout the year, although bottom trawling in- 

 dicated some horizontal dispersal shoreward in summer and back to deeper water 

 in fall. 



INTRODUCTION 



The fish population of Lake Michigan has 

 changed dramatically since the sea lamprey 

 ( Petromyzon marinus ) became plentiful, and 

 the valuable food species subsequently de- 

 clined (Hile, Eschmeyer, and Lunger, 1951; 

 Hile and Buettner, 1955; Moffett, 1957; and 

 Smith, 1964). The commercial fishery in the 

 southern portion of the lake was based origi- 

 nally on lake trout ( Salvelinus namaycush ), 

 whitefish ( Coregonus clupeaformis ), and some 

 chubs ( Leucichthys spp.), particularly the 

 larger species such as black fin cisco ( L . 

 nigripinnis ) and deepwater cisco (L. johnan- 

 nae ). With the decline or disappearance of 

 these choice species, emphasis shifted to an 

 alnnost exclusive chub fishery based on the 

 medium- sized species: longjaw (L. alpenae), 

 shortjaw (L. zenithicus ), shortnose (L. reig- 

 hardi ), and kiyi (L. kiyi ). These species have 

 now either disappeared or are found only in 

 small numbers. The chub population is now 

 dominated by the bloater (L. hoyi), which is 



the smallest and slowest growing of the chub 

 species. The recent explosive invasion of the 

 alewife (fig. 1) has had additional effects on 

 the fauna. Today the struggling gill net fishery 

 is based on the few remaining larger chubs 

 and a sporadic yellow perch population. Thus, 

 to survive, fishermen must now turn to the 

 abundant low- value species such as alewives 

 and bloaters. A limited trawl fishery has 

 become established in southern Lake Michi- 

 gan- -three vessels now are operating in Michi- 

 gan waters, and eight vessels in Wisconsin 

 waters. In 1965 these vessels landed over 12 

 million pounds of fish, primarily alewives 

 and chubs 



The Bureau of Commercial Fisheries be- 

 gan bottom trawl explorations in Lake 

 Michigan in August I960 (Gordon, 1963). 

 After the construction of the R. V. Kaho in 

 1961 for exploratory fishing and gear re- 

 search, explorations have continued since 

 1962. This paper summarizes explora- 

 tions from 1962 to 1965 in southern Lake 

 Michigan. 



