are usually there in the summer.^ Alewives move 

 to the bottom in increasing numbers throughout 

 their third year (age-group TI) and make up a 

 sizable portion of the bottom catch by late summer. 

 Fish older than 3 years may be found on the bot- 

 tom at all times, but usually are also at midlevels 

 in varying proportions, depending on the season. 



The midwater distribution of alewives, espe- 

 cially when the Lake is homothermous, is poorly 

 known. When the Lake is stratified, young of the 

 year apparently are confined to the epilimnion ex- 

 cept in the fall. Concentrations of older fish have 

 been found in the thermocline. Many, especially 

 those older than yearlings, are also regularly above 

 the thermocline and at times are probably present 

 in large numbers a few fathoms off the bottom in 

 areas where the bottom water is warm. In mid- 

 August 1965, alewives older than 1 year were 

 found in midwater from shore to shore in south- 

 ern Lake Michigan. 



The following discussion of bottom distribution 

 is based almost entirely on alewives caught in 

 standard series. Young of the year are referred 

 to as "young" and older fish arbitrarily as "adults." 



Young 



Young alewives were first caught in the stand- 

 ard series on October 14 (table 2). At that time 

 they were at all bottom depths to 25 fathoms at 

 temperatures of 11.5 to 12.4° C. The temperature 

 at the shallowest depth at which they were absent 

 (30 fathoms) was 6.0° C. On November 4, when 

 the cold bottom water (6.1° C.) had moved shore- 

 ward to 25 fathoms, yomig alewives were taken 

 only at depths of 20 fathoms and less in bottom 

 temperatures of 10.8 to 11.9° C. Largest catches, 

 however, were deeper in November than in Octo- 

 ber; apparently a movement away from shore 

 was in progress, but fish in the deepest water had 

 moved shoreward to avoid cold water. 



Young alewives in the November series were 

 larger in deeper water. The average length ranged 

 from 2.0 to 2.2 inches (5.1 to 5.6 cm.) in the tows 

 at 3 to 10 fathoms and 2.6 to 2.9 inches (6.6 to 7.4 

 cm.) at 12 to 20 fathoms. This size-depth relation 

 was not apparent in the October seriesj but was 



Table 2. — Numbers of young-of-lhe-year (0 group) alewives 

 and young-of-ihe-year smelt taken in 10-minute trawl tows 

 at various depths, October 14 and November J,, 1984 



[No young-of-the-year alewives or smelt were caught at 30, 35, 40, 45, and 50 

 fathoms on either date; none were taken in standard series on Feb. 13, 

 Mar. n, Apr. 15, May 5, May 26, June 16, July 7, July 28, and Aug. 21] 



1 Large numbers of yearling alewives -were concentrated between 

 the breakwalls at the mouth of the Kalamazoo River at Saugatuck 

 in early July 1967. Commercial fishermen, who trawl for adult 

 alewives between breakwalls in the spring and early summer, 

 reported that such large numbers of small ones had not aiipeared 

 before. 



pronounced in sampling off several ports in south- 

 eastern Lake Michigan in 1967. 



Adults 



Adult alewives showed a more striking seasonal 

 migration than any other species. In February they 

 were concentrated in deep water (table 3). They 

 were taken at 30 to 50 fathoms in the standard 

 series of February 13. The catches increased 

 sharply with depth; 74 were caught at 30 fathoms 

 and 11,267 at 50 fathoms. (Other catches by the 

 R/ V Kaho and reports from commercial fishermen 

 indicate that concentrations in winter may extend 

 at least to 70 fathoms.) By March 11 the beginning 

 of a shoreward movement was evident. A few ale- 

 wives were as shallow as 15 fathoms, but concen- 

 trations were still at the greatest depths. Movement 

 toward shore was rapid after March 11 ; by April 

 15 the largest concentration was at 10 fathoms, 

 and relatively few were taken at depths greater 

 than 17 fathoms. The shoreward movement was 

 probably greatest in the latter portion of the March 

 11 to April 15 period. Commercial fishermen re- 

 ported heavy concentrations of alewives at 35 fath- 

 oms on April 7; on April 11 the R/V d-sco took 

 few at 35 fathoms but large numbers at 20 fathoms. 

 Adult alewives were present in large numbers at 3 

 fathoms on May 5 and 26. Concentrations probably 

 extended into still shallower water. Catches also 

 were large at 12 and 15 fathoms on May 5 and at 

 15 to 20 fathoms on May 26. Most alewives on the 

 bottom remained in shallow water throughout the 



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