1/2-hour drag) were taken on all but two 

 cruises, 1 and 28. Cruise 1, a shakedown 

 cruise, apparently missed the right fishing 

 depth. Cruise 28 fished only off Ludington and 

 Manitowoc at a time when alewives were dis- 

 persed vertically. Of the 84 depth series, 33 

 or nearly 40 percent had con-imercially sig- 

 nificant catches of alewives; however, in the 

 3 8 depth series covering a range of 40 fathoms 

 or more, 22 or nearly 60 percent had com- 

 mercially significant amounts of alewives. 

 Ninety-five or 12 percent of the total drags 

 had a catch rate of 500 pounds or more of 

 alewives per one-half hour. The largest catch 

 of alewives during the study was 3,800 pounds 

 taken in 15 minutes off Manitowoc on cruise 

 17 (table 9). The best catch rate for an in- 

 dividual drag was 1,500 pounds in a 5-minute 

 drag off Port Washington also on cruise 17. 



Similar to other anadromous fishes, the 

 alewife exhibited very pronounced seasonal 

 movenaents in southern Lake Michigan. The 

 trend of these seasonal movements is dis- 

 closed by records of fishing depths by com- 

 mercial trawlers (fig. 4) and catch rates of 

 the Kaho during selected periods (fig. 5). In 

 general the seasonal depth availability to 

 bottom trawls appears to follow the same 

 pattern throughout southern Lake Michigan 

 and can be identified in six phases as follows: 



1. From the first of the year to about the 

 second week in April, alewives concen- 

 trate on the bottom in water 35 fathoms 



and deeper. Throughout February the 

 highest catches are taken in 45 fathoms 

 or deeper, and alewives appear to form 

 isolated schools because they are only 

 taken in certain areas. Late in the period 

 few alewives are taken at less than 30 

 fathoms, although at the beginning of the 

 period some are taken at shallower 

 depths. 



About the second week in April, alewives 

 begin a massive spawning migration that 

 continues through mid- May. During this 

 period large quantities of alewives can 

 be taken easily on the bottom over a wide 

 depth range. The start of the spawning 

 run is not uniform throughout the south- 

 ern portion of the lake and may lag for 

 several weeks or more. The shoreward 

 movement begins first in the extreme 

 southern portion of the lake and con- 

 tinues at successive locations north- 

 ward. The inshore move appears to 

 happen sooner on the west shore than 

 at the same latitude on the east 

 shore. 



In southern Lake Michigan most of the 

 spawning occurs from mid- May through 

 June; however, some spawning apparently 

 takes place into August. During mid- May 

 to June, alewives are taken in large 

 quantities in rivers and along the beaches 

 in 5 fathoms or less, and very few ale- 

 wives are on the bottom in water deeper 

 than 5 fathoms. 



Table 9. — Largest catch of alewives for each cruise in southern lake 



Michigan, 1962-65 



■"■ Five l/2-hour drags caught 10 pounds each at scattered locations between 25 

 and 40 fathoms. 



11 



