From among those sanples examined for length, one complete 

 collection v/as taken at random and the Treight of all individuals 

 was determined to the nearest tenth of a gram upon an Ohaus diet- 

 ary scale. This sample consisted of 216 migrants taken in the 

 Carp Lake River trap on November 20, 19U8. These individuals 

 varied from 2,3 grams to 8. It grams in vc^ight and averaged I4.I 

 grams; their total length ranged from 121 millimeters to 172 

 millimeters -with a mean of llj.3«0 millimeters. 



Observations on habits and behavior 



One of the most striking characteristics of the doivnstream 

 movement of newly-transformed sea lampreys is the abruptness ivith 

 which large numbers of individuals suddenly leave the mudbanks and 

 move downstream. Under the impetus of rising waters, a virtual 

 emergence takes place and hordes of the new adults travel down- 

 stream on the rise and crest of the floodwaters. This surge of 

 movement downstream frequently ends as suddenly as it began. 



Most of the individuals observed in migration displayed little 

 deliberate effort towards accelerating their passage doTmstream. 

 Such swimming activities as they affected in a downstream direction 

 were casual and intermittent; some were seen to be drifting tail- 

 first upon occasion. The whole movement downstream is character- 

 istically passive on the part of the sea lamprey. The celerity with 

 which these emergences of transformed individuals travel down to 

 the lakes must therefore be attributed to the increased vol\jme and 

 velocity of the stream when such movements occur. 



Field observations and laboratory examinations indicate that 

 very few young sea lampreys attempt to feed Tshile passing davm- 

 stream to the "big" lakes. An exception to this occurs, of course, 

 in those watersheds ivhere large, inland lakes provide conditions 

 suitable for the parasitic phase; at least two such lakes occur 

 in Michigan. "Where smaller inland lakes interrupt the do-vmstream 

 journey, the migrants apparently pass through such waters without 

 attacking the resident fish species. For example, each year many 

 thousands of recently-transformed adults pass through Ocqueoc Lake 

 on their way down the Ocqueoc River to Lake Huron. Since 19^7, 

 many fish taken in all seasons of the year from this lalce have been 

 examined and none have borne scars that could be attributed to down- 

 stream migrants. Furthermore, the digestive tracts of 216 recently- 

 transformed individuals taken on November 20, 19lj.8, in the Carp 

 Lal^e River trap ivere opened and none showed any evidence of having 

 attempted their initial feeding after transformation (length and 

 weight data for this sample presented in a preceding section). 



Were it habitual for young migrants to begin feeding before 

 reaching the big lakes, many reports would have been forthcoming 

 of resident stream fish bearing young sea lampreys or their scars. 



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